Syrian officials say twin suicide bombings in Damascus have killed at least 44 people and left at least 150 others injured.
State television reports that two bombers used vehicles packed with explosives to attack a pair of state security facilities in the capital on Friday.
The state-run SANA news agency displayed graphic photos that it said showed victims of what it called "terrorist attacks." The news agency also said Syrians had gathered in Damascus and several other cities to protest the bombings.
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Witnesses reported hearing heavy gunfire after the explosions.
Syrian officials said al-Qaida militants may be responsible for the attacks. A deputy foreign minister, Faysal Mekdad, told reporters the bombings are proof of the government's longtime claims that terrorists are behind much of the violence linked to opposition protests.
"All who stand behind these criminals in Syria and defend and support these crimes are considered responsible for the terrorist acts," he was quoted as saying.
The bombings have come on the heels of the arrival of an Arab League advance delegation that is setting up an observer mission in Syria. News reports say some delegation members visited the bombing sites.
Syrian opposition groups called for mass protests on Friday against the Arab League observers, who intend to monitor whether the government follows through on its promise to stop the crackdown on dissent.
Opposition groups say the government is only allowing the monitors as a stalling tactic to prevent a new round of international sanctions against Syria for its crackdown on dissent.
Also, activists said security forces killed at least 14 more protesters across Syria on Friday.
Meanwhile, the U.S. condemned Friday's bombings and said Syria must not allow the attacks to hamper the Arab League's monitoring mission. Lebanon also condemned the blasts.
The Syrian government has defended its harsh crackdown on pro-democracy protesters by saying it is fighting "armed terrorists," though Friday's bombings appear to be the first of their kind since the anti-government uprising began in March.
The advance team of Arab League observers that arrived Thursday is laying the groundwork for a larger group of delegates that is set to arrive Monday.
The Arab League has also been urging Syria to withdraw its security forces from neighborhoods and begin talks with the opposition.
On Thursday, Syria said more than 2,000 security force members had been killed since the uprising began. The United Nations says at least 5,000 people have been killed.
Some information for this report was provided by AP, AFP and Reuters.