ISTANBUL -- Turkey's Parliament approved a motion Thursday that authorizes further military action against Syria, as Turkey began its second day of shelling targets within Syria in response to a mortar attack that killed five civilians.
The measure, which was ratified after several hours of a closed-door session in the capital, Ankara, permits cross-border raids, although senior officials insisted that NATO ally Turkey did not want a war with its Arab neighbor -- an escalation that could turn Syria's bloody civil strife into a regional conflict with international involvement.
The motion read, in part, "The ongoing crisis in Syria affects the stability and security in the region and now the escalating animosity affects our national security," according to the semiofficial Anatolian News Agency.
The Turkish military pounded targets inside Syria on Thursday in retaliation for the mortar attack a day earlier that killed five civilians in Turkey.
Local news reports said Turkish shells fell inside Syria on at least 10 occasions after midnight, landing near the border town of Tel Abyad, some six miles inside Syrian territory, across a historic fault line where modern Turkey abuts Arab lands that once formed part of the Ottoman Empire.
State television said the shelling continued until dawn with four more barrages until the guns fell silent around 6:45 a.m. Activist groups in Syria said the shelling killed several Syrian government soldiers.
The exchanges sent tremors across a region fearful that the mounting violence in Syria would spill into neighboring countries. Ibrahim Kalin, a senior aide to Prime Minister Recep Tayyip Erdogan of Turkey, wrote on Twitter feed: "Turkey does not want war with Syria. But Turkey is capable of protecting its borders and will retaliate when necessary." In a separate message, he said: "Political, diplomatic initiatives will continue."
The assurance came as western European leaders who have joined Turkey in supporting rebel forces in Syria sought to prevent the border clash from flaring out of control.
Catherine Ashton, the European Union's foreign policy chief, criticized Syria for Wednesday's mortar bombing, but urged restraint "on all sides." The British Foreign Secretary, William Hague, said Turkey's response was "understandable, an outrageous act has taken place, Turkish citizens have been killed inside Turkey by forces from another country." He added to Reuters, "So we express our strong solidarity with Turkey, but we don't want to see a continuing escalation of this incident."
The North Atlantic Treaty Organization, to which Turkey belongs and whose charter calls in some cases for collective action when one of its members is targeted militarily, met Wednesday night to discuss the crisis.
At the Security Council, Russia blocked an attempt to issue a strongly worded statement condemning Syria for the attack, diplomats said, reinforcing council divisions over the conflict that have been in play since the uprising started in May 2011.
Azerbaijan, working on a request from Turkey, had proposed a draft statement on Wednesday that also expressed alarm about the conflict spilling into neighboring countries, a long feared escalation.
While the original text explicitly condemned the Syrian forces, Russia proposed revising it to refer to shelling from Syrian territory, diplomats said, despite the fact that Damascus has already apologized. It also removed the phrase that the episode constituted a serious "threat to international peace and security," standard language which signaled that the council expected to stay involved.
Council diplomats continue to wrangle over the wording.
Russia and China both previously vetoed three Security Council resolutions addressing the Syria conflict and have urged Western powers to put more pressure on the anti-government forces to stop fighting. Russian protection of the Assad regime is one reason cited by analysts for the Syrian government's refusal to implement any kind of cease-fire.
Syria has intimated that it never intended to strike inside Turkey, and its minister of information, Omran al-Zo'aby, suggested on state television that Syria was defending against a regional threat that could affect Turkey and Syria.
"The Syrian-Turkish border is a long one and is being used for smuggling weapons and terrorists," he said, adding that in response to border episodes, neighboring countries should act "wisely and rationally and responsibly, especially in cases of the presence of armed terrorist groups who have their different agendas that are not targeting the Syrian national security but the regional security."
It was unclear if the shell that struck Turkey was fired by government forces or by rebels fighting to oust the government of President Bashar al-Assad of Syria, but Turkey believed it came from a government position, Turkish analysts said. Turkey has called in an emergency session at the North Atlantic Treaty Organization and revised its engagement rules in a way to allow military action when its national security is threatened. It refrained from direct military engagement in response to the downing of its jet in international airspace.
"Turkey is not a country wishing for war, but peace," Omer Celik, a senior government official, said on Thursday in a televised statement before the parliamentary debate, but he called on all parties to support what he called a measure to protect Turkey's sovereignty.
While Syria has offered condolences to Turkey over the death of its civilians and has said an investigation was under way, Mr. Celik said that the "words of a regime killing its own people cannot be taken into account."
He called the government of Mr. Assad "a massacre network" and declared: "We are not in a position to take seriously anything this massacre network says."
In a statement carried by the semiofficial Anatolian News Agency on Wednesday, Mr. Erdogan's office said Turkish forces used radar to identify targets to be hit after the "atrocious attack" from Syria "in accordance with rules of engagement."
While suicide bombers killed dozens on Wednesday as violence surged in Syria's largest city, Aleppo, it was the cross-border strike that raised the stakes in a civil war that has left tens of thousands dead and forced more than a million people from their homes. The war has defied exhaustive diplomatic efforts by the global community. The events may increase pressure for the West to take military action, something Turkey has supported. The United States and its allies have balked at engaging in another armed conflict in the Muslim world that would be far riskier than NATO's intervention in Libya, which helped oust Col. Muammar el-Qaddafi.
"The conflict in Syria is spilling well over its borders," said Andrew Tabler, a Syria analyst at the Washington Institute for Near East Policy. "I don't see how the Obama administration continues policy as usual after this."
But in the fog of war that has settled over Syria, where allegiances and motives are uncertain and a bloody stalemate has taken hold, some observers said they could not help wondering if the episode had been orchestrated by one side or another. The rebels have implored NATO to provide a no-fly zone or havens, and Mr. Assad may feel he can rally his supporters against foreign invasion, experts said. "Various parties are trying to pull Turkey into the conflict," Atilla Sandikli, the director of the Wise Men Center for Strategic Studies in Ankara, Turkey, said on the Turkish channel NTV.
In Washington, George Little, the Pentagon press secretary, called the Syrian attack on Turkish territory "yet another example of the depraved behavior of the Syrian regime, and why it must go."
Secretary of State Hillary Rodham Clinton said she was "outraged" by the mortar attack in Turkey.
After its meeting, NATO issued a statement saying the alliance continued "to stand by Turkey and demands the immediate cessation of such aggressive acts against an ally, and urges the Syrian regime to put an end to flagrant violations of international law."
Turkey's military strike within Syria, which represented a further deterioration of relations between the onetime allies, came after several huge explosions struck a government-held district of Aleppo. The blast killed dozens of people and filled the streets with rubble in a square near a public park, according to video, photographs and reports from the Syrian government and its opponents.
At least two explosions, which both sides said appeared to be car bombs, struck Saadallah al-Jabiri Square near an officers' club and two government-owned hotels that residents said had housed pro-government militiamen who had essentially taken over the square. Another explosion struck near the chamber of commerce in nearby Bab Jenine, both sides reported.
Jabhet al-Nusra, an insurgent group affiliated with Al Qaeda, claimed responsibility late on Wednesday for the suicide bombings, which caused anguish for government supporters and opponents alike. The scale of Wednesday's bombings seemed to deepen Aleppo's sense of alarm and disgust, bringing expressions of horror and bewilderment from people on either side of the conflict.
"Oh, my God, the destruction is huge," an accountant who works nearby, who asked to be identified only by his first name, Rami, said on his cellphone as he tried without success to approach the square, which he said was barricaded by security forces. Back in his office, listening to gunfire still echoing through the area, he wrote on Facebook: "My soul has died and my body is waiting for its turn."
One Syrian activist, who uses the pseudonym Anonymous Syria, wrote on Twitter: "Whoever is behind those explosions is a terrorist if civilians were killed. Whether it is the regime, Al-Nusra brigade or the Free Syrian Army."
In the square, men simply shouted obscenities and cursed "the terrorists' fathers." Their voices could be heard in the background as another man videotaped the bomb scene for a pro-government YouTube channel, panning over the corpses of two men in crisp camouflage uniforms who he said were would-be suicide bombers killed by security forces.
Before the retaliatory strike by Turkey, the government said in a statement that its foreign minister, Ahmet Davutoglu, had consulted Lakhdar Brahimi, the United Nations and Arab League joint special envoy to Syria, as well as Ban Ki-moon, the secretary general of the United Nations. The prime minister's statement said the strike was within the rules of engagement established after the Syrian military shot down a Turkish warplane in June, killing two pilots in international airspace over the Mediterranean Sea. Syria had claimed the plane was flying over its own territory.
"This last incident is pretty much the final straw," said Bulent Arinc, Turkey's deputy prime minister, as quoted by the Anatolian News Agency. "There has been an attack on our land and our citizens lost their lives, which surely has adequate response in international law."
Tim Arango and Sebnem Arsu reported from Istanbul, and Anne Barnard from Beirut, Lebanon. Reporting was contributed by Alan Cowell from Paris, Hala Droubi, Hania Mourtada and Hwaida Saad from Beirut, Neil MacFarquhar from the United Nations and Thom Shanker from Washington.
This article originally appeared in The New York Times.