TRIPOLI, Lebanon -- Car bombs exploded with catastrophic force outside two Sunni mosques in this northern Lebanon city on Friday as many worshipers were leaving prayers, killing dozens of people and wounding hundreds. The bombings were a major escalation of sectarian violence in Lebanon, a country deeply unsettled by the conflict in neighboring Syria, and reinforced fears that the Middle East could be plunging into unbridled Sunni vs. Shiite warfare.
President Michel Suleiman cut short a visit abroad to meet with security officials on the double blast and exhorted them to "deploy their efforts to reveal the perpetrators and the instigators." Lebanon's prime minister-designate, Tammam Salam, said in a statement that "the Tripoli crime is an additional indicator that the situation in Lebanon has reached a very dangerous level."
Witnesses and Lebanese media said the double blast hit the Taqwa and Al-Salam mosques, which are on opposite sides of the city, at around 1:38 p.m. Tripoli's mayor, Nader Ghazal, was quoted by Lebanese news media as saying at least 50 people were killed. The Lebanese Red Cross said more than 500 were wounded.
The bombings easily eclipsed the death toll and destruction from a bombing a week earlier in southern Beirut that had targeted Hezbollah, the Shiite militant organization that has aligned with Syria's government against a Sunni-led insurgency, which has contributed to an increasing polarization in Lebanon.
With deadly sectarian violence now regularly convulsing Iraq as well, a broad area of the region stretching from the Mediterranean east to Baghdad and beyond has become a battleground between Sunnis and Shiites, the major Islamic sects. Political historians said the Tripoli bombings would not go unanswered.
"This was an upping of the ante," said Mona Yacoubian, the senior Middle East adviser at the Stimson Center, a nonpartisan research group in Washington. "I think we're seeing the contours of this arena forming in front of our eyes."
The first car bomb hit about 50 yards from the gates of the Taqwa mosque, setting dozens of cars and a nearby building on fire and shattering the windows of surrounding buildings. The blast snapped the trunks of palm trees and left a crater in the street that punctured a water main, flooding the street. On the roof of the mosque's entryways sat the carcass of blown-up car that people nearby at the time said was the bomb car, hurtled into the air by the blast.
The second blast near the Al-Salam mosque blasted a six-foot-deep hole in the asphalt and shattered the windows of apartment towers down the block.
There were no immediate claims of responsibility for the blasts, but the Taqwa mosque was where Sheik Salem al-Rafei, an outspoken Sunni preacher, had inveighed against Hezbollah and had exhorted worshipers to support the Sunni insurgency trying to topple Syria's president, Bashar al-Assad.
Many Taqwa worshipers said they believed their mosque had been targeted because of Sheik Rafei. A large banner hung on the mosque's fence bore photographs of three men killed in the battle for the border city of Qusayr, Syria, nearly three months ago, in which Hezbollah fighters joined the Syrian Army to defeat Sunni insurgents ensconced there in what is widely viewed as a turning point in the Syria conflict. Text next to their faces said they had been "martyred defending the dignity and pride of the nation."
Sheik Rafei was not hurt in the bombing, worshipers said, but efforts to contact him were not immediately successful.
One Taqwa worshiper, Saad al-Din Turkomani, 27, said he was inside the mosque listening to Skeik Rafei preach when the explosion blew out the windows and filled the hall with smoke. He said he saw the bombings as a response to last week's bombing in a Hezbollah stronghold in Beirut.
"It was a response to our sheik," he said. "One from our side went to them, so they sent two of theirs to us. They are making us pay the price."
Like most people in Tripoli, he expected more sectarian violence. "We are entering a hard stage," he said. "Things are lighting up between the Sunni and the Shia."
Denying responsibility, Hezbollah condemned the bombings. "These two terrorist explosions come as a translation of the criminal plot that seeks to sow the seeds of discord among the Lebanese and drag the country to internal strife under the headline of sectarianism and religious differences," the group said in a statement. Accusing unnamed foreign forces of backing the attacks, it said such mayhem benefited "the evil regional international plan that wants to break up our region and drown it in oceans of blood and fire."
Video of the scenes broadcast just minutes after the attacks showed thick smoke billowing across Tripoli, a Mediterranean port city. One video clip posted on YouTube showed angry crowds converged outside the smoking Taqwa mosque.
[Video: Watch on YouTube.]
A second video clip, apparently from a security camera inside the Al-Salam mosque, showed the precise moment of an enormous blast as worshipers were still praying.
[Video: Watch on YouTube.]
Since the uprising started in Syria more than two years ago, fighting in Lebanon has flared sporadically, with Tripoli a tinderbox because of sectarian tensions similar to those across the border. The recurring street fights pit Sunni Muslims, who support the Syrian uprising, against members of the Alawite sect, an offshoot of Shiite Islam to which Mr. Assad belongs.
Hwaida Saad and Ben Hubbard reported from Tripoli, Lebanon, Reporting was contributed by David Jolly from Paris, and Christine Hauser and Rick Gladstone from New York.
This article originally appeared in The New York Times.