At least 27 people were killed after two explosions rocked security compounds in the Syrian capital of Damascus on Saturday, al Jazeera television reports.
Ninety-seven others were wounded in the blasts, which state TV described as "terrorist" attacks.
It said intelligence and police buildings were targeted and that initial reports suggest the explosions were caused by car bombs.
Most of the dead are believed to be civilians.
The UK-based Syrian Observatory for Human Rights also said security buildings were hit.
The explosions came two days after the first anniversary of the country's anti-government uprising, which the UN says has left more than 8,000 people dead.
Dozens of people were killed in explosions in Damascus in December and January.
On Friday, he UN and Arab League envoy on Syria, Kofi Annan, said he was sending UN teams to Damascus this weekend to discuss establishing a new international monitoring mission.
A UN expert team will arrive in Syria on Sunday, Russian Deputy Foreign Minister Gennady Gatilov wrote on his Twitter account on Saturday.
Turkey said on Friday it is considering imposing a "buffer zone" onalong its border with Syria to protect refugees fleeing government forces.