Two "terrorist explosions" struck security targets in the Syrian capital Damascus today, killing a number of civilians and security forces, the state news agency said.

The report said the blasts were caused by car bombs that hit the aviation intelligence department and the criminal security department at about 7.30am local time.

The state-run news agency, SANA, posted gruesome photographs of the scene, with mangled and charred corpses, bloodstains on the streets and twisted steel.

One year into the Syrian revolt, the fight to oust President Bashar Assad is transforming into a nascent civil war. The regime says it is fighting foreign terrorists and armed gangs, denying there is a popular will behind the revolt.

But Assad's opponents say they have been forced to carry weapons because the government used tanks, snipers and machine guns to crush peaceful protests.

Syria has seen a string of suicide bombings, the last major one on February 10, when twin blasts struck security compounds in the government stronghold city of Aleppo, killing 28 people.

Damascus, another Assad stronghold, has seen three suicide previous bombings since December.

The regime has touted the attacks as proof that it is being targeted by "terrorists." The opposition accuses forces loyal to the government of being behind the bombings to tarnish the uprising.

Nobody has claimed responsibility for the explosions.

The UN estimates that more that 8,000 people have been killed since the uprising against Assad began last March.

In recent weeks, Syrian forces have waged a series of heavy offensives against the main strongholds of the opposition - Homs in central Syria, Idlib in the north and Daraa in the south. In the assaults, the regime has seemed to depend on select units and has relied heavily on the minority Alawite sect, to which Assad and the ruling elite belong. That may be out of worries over signs that some Sunni army conscripts have refused to fire on civilians.

Sunnis are the majority in the country of 22 million and make up the backbone of the opposition.

Diplomatic efforts to solve the crisis have so far brought no result. But UN envoy Kofi Annan told the Security Council in a briefing Friday that he would return to Damascus even though his recent talks with Assad saw no progress in attempts to cobble together peace negotiations between the two sides.