Two suicide car bombers struck Syrian capital Damascus today, killing 44 people according to an interior minister spokesperson.
The Syrian government blamed al Qaeda for the blasts, which hit two security compounds.
The blasts came a day after the arrival of Arab League officials to prepare for a monitoring team that will check whether President Bashar al-Assad is implementing a plan to end the bloodshed.
Activists said they were surprised at the speed with which authorities levelled accusations at al Qaeda, barely an hour after the explosions shook a central district which residents said is well-policed and has restrictions on traffic movement.
"I believe the blast was engineered by the Syrian regime," Lebanon's anti-Syrian former prime minister Saad al-Hariri said.
Syria has generally barred foreign media from the country, making it hard to verify accounts of events from either side.
However analysts said authorities were unlikely to have staged an attack that only serves to highlight their vulnerability.
Syrian President Assad has unleashed tanks and troops to try to crush nine months of street protests inspired by other Arab uprisings this year.
Mainly peaceful rallies are now increasingly eclipsed by an armed insurgency against his military and security apparatus.
However today’s blasts in central Damascus signalled a dramatic escalation in violence, which Syrian authorities blame on armed groups they say have killed 2,000 soldiers and security force members this year.
The United Nations says Assad's crackdown has killed 5,000 people.
The interior ministry spokesman said 166 people were wounded by the explosions.
It broadcast footage of mangled bodies being carried in blankets and stretchers into ambulances.
Foreign Ministry spokesman Jihad Makdesi said the attacks were carried out by "terrorists (trying) to sabotage the will for change" in Syria, and followed warnings from Lebanon that al Qaeda fighters had infiltrated Syria from Lebanese territory.
The United States condemned the attacks, saying there was "no justification for terrorism of any kind" and that the work of the Arab League should not be hindered.
There was no immediate claim of responsibility.
Al Qaeda are Sunni Muslim militants. Assad and Syria's power elite belong to the Alawite branch of Shi'ite Islam while the majority of Syrians, including protesters and insurgents, are Sunnis.
Assad's opponents said the attack could have been staged to drive home the government's argument.
