BEIRUT, Lebanon -- Some of the worst violence in months racked Syria on Monday with residents of southern Damascus fleeing heavy shelling, several smaller towns shattered by air attacks and at least two car bombs erupting.
The Local Coordinating Committees, a collection of activist organizations across Syria, said the daily toll reached at least 159, including 72 killed in Idlib, and 47 in Damascus and its suburbs.
People in Damascus, the capital, said the fighting was the fiercest they could remember since July, with thousands of people fled as a Palestinian faction that supports the Assad government skirmished with government opponents in three southern neighborhoods.
"It's a real war," said an activist reached in southern Damascus via Skype, who used only one name, Eman, for her own safety. "Explosions, bombing and gunfire, and of course the helicopters, which have become part of the sky in Damascus now, like birds," she said.
The fighting, escalating over three days, ignited the quarters of Yarmouk and Tadamon, both heavily Palestinian, as well as Hajjar al-Aswad, a long-embattled center of resistance to the government.
Syria took in large numbers of Palestinians who fled their homes at the founding of Israel, and they and their descendants number about 450,000 now. Many have sided with those leading the uprising, but the Popular Front for the Liberation of Palestine-General Command, a faction with a prominent role in the neighborhoods, still supports the government. Much of the fighting involved Popular Front units, backed by government artillery. Artillery rounds fired from the military airfield in Mezze slammed into the area repeatedly, activists said.
Yarmouk, founded as a Palestinian refugee camp in 1957, gradually became a residential district barely distinguishable from the rest of greater Damascus. A Facebook page focused on camp news published a statement from the Popular Front group saying it had thwarted an infiltration of the area by government opponents.
"When the terrorists failed to enter, they fired mortars killing a large number of martyrs and wounding a lot of people," the statement said.
Civilians have been fleeing in droves. Small artillery hit a minibus carrying people trying to escape from Yarmouk, killing five of them. Each side blamed the other for that strike.
Displaced families have started camping in back gardens or schoolyards, Eman said.
A car bomb exploded in Mezze 86, a Damascus neighborhood on the slopes below the official palace that houses the offices of President Bashar al-Assad. The area is heavily populated by families linked to the security forces, which Mr. Assad's Alawite minority dominates. Pictures posted on Facebook showed a large black column of smoke rising from the area.
The Free Syrian Army claimed responsibility for that attack, saying in a statement that it targeted military officers and members of the armed militias who fight for the government.
The bomb, a booby-trapped car, exploded in Bride Square, killing at least 11 people and wounding more than 30, some of them critically, said the Syrian Observatory for Human Rights, which tracks the conflict from abroad.
The official news agency, SANA, also put the death toll at 11 killed but said at least 56 were injured. The explosion ignited other cars and caused widespread destruction, it said.
Accounts differed more sharply on another car bombing, outside a government-owned Rural Development Center near Hama. The rebels and activists reported that dozens of soldiers were killed; the government said just two civilians had died.
The Syrian Observatory, which tracks the conflict from abroad, said that Jabhet Al-Nusra -- known as a jihadist organization -- and other rebel groups in the region collaborated to explode a car bomb at a government checkpoint in a village near Hama, killing at least 50 soldiers. If true, that would make it one of the single deadliest attacks against the government since the uprising started in March 2011.
The accounts from the observatory and rebel groups stated that the military had taken over the development center to house military units. Checkpoints in rural areas often serve as rudimentary bases for the government, with large numbers of men and equipment.
"They targeted one of the biggest checkpoints in the region," said Ahmad Raadoun, a member of the Free Syrian Army in the Hama suburbs who was reached by Skype. "It's a big building where the regime forces were headquartered."
Mr. Raadoun said he was about 20 miles from the site, which he said was in the village of Ziyara. He said the bomb caused extensive casualties and other damage.
The official account from SANA said a suicide bomber in a vehicle killed two civilians and wounded 10 others. The government routinely refers to rebels as terrorists and has repeatedly singled out the Jabhet group as a terrorist organization.
In its daily roundup of violence around the country, SANA also said that government forces clashed with "terrorists" in the eastern city of Deir al-Zour, and in Aleppo, in the north.
Activist organizations reported a number of airstrikes around the country, with the toll particularly high in the northern towns of Harem and Kafr Nabl, both near Idlib.
Kafr Nabl has gained a reputation throughout the conflict for its savvy demonstrations. For instance, villagers often carry signs in English to attract international support.
But the mood was starkly different on Monday, with local activists saying that a government airstrike had killed at least 17 people and that more were buried under the rubble.
Video accounts cannot be independently confirmed, but three videos posted on Monday from Kafr Nabl all had similar scenes and the same people seen mourning over corpses covered with bloody blankets and tarpaulins on the main street.
"They're gone! They're gone!" shouted one middle-age man with white hair, seemingly distraught over the death of his two sons. "Where is Waleed? Where is he? I just want my kids, my two kids they are waiting for their mother to come."
One extremely graphic video posted from the village of Kafr Nabl, near Idlib, shows bloodied victims dumped into a truck in the aftermath of what was described as an aerial assault. A shot of the main street shows flames leaping from vehicles and residents running around in panic. At least five men and one woman died, the Syrian Observatory said, but more victims were believed buried under the rubble.
At the United Nations on Monday, a top relief official said the organization's aid effort in Syria "is very dangerous and very difficult." The official, John Ging, director of operations of the Office for the Coordination of Humanitarian Affairs, told reporters at a news conference that the United Nations was supplying 1.5 million people in Syria with food and that nearly half was being delivered into areas of conflict, but "there are areas beyond our reach, particularly areas under opposition control for quite a long time."
In Rome, the World Food Program, the world's largest anti-hunger aid agency, announced that its executive director, Ertharin Cousin, would be visiting Lebanon and Jordan on a three-day trip starting Tuesday to assess the needs of the growing Syrian refugee populations in those countries. She will inspect food distribution points in Lebanon's Bekaa Valley and in Jordan's Zaatri camp near the Syrian border.
Hania Mourtada contributed reporting from Beirut; Hala Droubi from Dubai, United Arab Emirates; and Rick Gladstone from New York.
This article originally appeared in The New York Times.