DAMASCUS - Two suicide car bombers killed 55 people and wounded 372 in Damascus on Thursday, state media said, the deadliest attacks in the Syrian capital since an uprising against President Bashar al-Assad began 14 months ago.
The blasts further shredded a ceasefire that was declared by international mediator Kofi Annan on April 12 but which has failed to halt bloodshed pitting Assad's security forces against peaceful demonstrators and an array of armed insurgents.
Opposition leaders said Annan's peace plan was dead, while Western powers insisted it remained the best way forward.
Annan himself condemned the "abhorrent" bombings and urged all parties to halt violence and protect civilians. "The Syrian people have already suffered too much," he said in a statement.
Syria's foreign ministry said the attacks were a sign that the major Arab state was facing foreign-backed terrorism and urged the U.N. Security Council to combat countries or groups supporting such violence.
"Syria stresses the importance of the UNSC taking measures against countries, groups and news agencies that are practicing and encouraging terrorism," the state news agency SANA quoted the ministry as saying in a letter to the U.N. body.
The near-simultaneous explosions hit the al-Qazaz district just before 8 a.m. (06:00 a.m. British time), residents said. One punched a crater three metres (10 feet) deep in the city's southern ring road. Bloodied corpses and body parts could be seen on the road.
State television also showed at least one overturned lorry. Walls of buildings on each side of the avenue had collapsed.
One resident reported limited damage to the facade of the nearby Palestine Branch Military Intelligence centre, one of the most feared of more than 20 Syrian secret police agencies. The huge walled complex was targeted by a 2008 bombing that killed 17 people and which authorities blamed on Islamist militants.
The opposition Syrian Observatory for Human Rights put the death toll from the bombings at 59 and said most of them worked for the security forces. No group has claimed responsibility.
The Interior Ministry vowed to "chase down the criminal killers and those who help or house them in their dens". It also appealed to citizens to pass on any information that might help.
MOUNTING DEATH TOLL
Rami Abdulrahman, head of the British-based Observatory, said 849 people - 628 civilians and 221 soldiers, of whom 31 were defectors - had been killed since the April 12 truce accord. The toll did not include Thursday's deaths.
The attacks occurred a day after a bomb exploded near U.N. observers monitoring the ceasefire, which state forces and rebels have both violated, and two weeks after authorities said a suicide bomber killed at least nine people in Damascus.
"This (Thursday's attacks) is yet another example of the suffering brought upon the people of Syria from acts of violence," said Major-General Robert Mood, leader of the U.N. monitors, who visited the scene.
Opposition to Assad, which began with peaceful protests in March 2011, has grown increasingly militarised. U.N. Secretary-General Ban Ki-moon said on Wednesday there was only a narrow window of opportunity to avert full-scale civil war.