Syrian authorities say a double suicide bombing in Damascus has killed at least 55 people and wounded another 370, making it the country's deadliest attack since an opposition uprising began 14 months ago.

State media say two suicide car bombers with 1,000 kilograms of explosives blew themselves up in quick succession in the capital's southern Qazaz district during Thursday's morning rush hour.

The blasts left a scene of carnage with charred vehicles and body parts covering the street. Witnesses say the attack appeared to target a Syrian military intelligence building and damaged its facade.

The Syrian government blamed the bombings on terrorists whom it says are behind the revolt against President Bashar al-Assad. But the main exiled Syrian National Council accused the government of orchestrating the attack to try to smear the opposition movement and scare away a U.N. observer mission.

There was no immediate claim of responsibility for the blasts.

Observer chief Robert Mood, a Norwegian general, visited the scene of the attack and condemned it.

“This is a terrible kind of violence that is deplorable. It is the kind of violence that is not deserved by the Syrian people.”

International peace envoy Kofi Annan, who oversees the U.N. monitors, called the double bombing “abhorrent.” In a statement, he said the Syrian people “have already suffered too much.”

Thursday's attack happened one day after a roadside bombing near the rebellious southern city of Daraa wounded 10 Syrian soldiers who were escorting General Mood and other U.N. monitors. The U.N. personnel were unharmed.

The United Nations says more than 9,000 people have been killed in violence related to the anti-government uprising which erupted in March 2011.

Meanwhile, vote-counting continues from Monday's parliamentary elections in Syria. Opposition groups have dismissed the elections as a sham.