Syrian army defectors have attacked an intelligence complex on the edge of Damascus, in the first reported assault on a major security facility in the eight-month uprising against President Bashar al-Assad.
Activists say members of the Free Syrian Army fired shoulder-mounted rockets and machine guns at a large Air Force Intelligence complex.
They say a gunfight ensued and helicopters circled the area.
Together with Military Intelligence, Air Force Intelligence is in charge of preventing dissent within the army.
The two divisions have been instrumental in a crackdown on the uprising against President Assad, which the United Nations says has killed 3500 people.
Turkish Prime Minister Recep Tayyip Erdogan has made his strongest denunciation yet of Syria's President Bashar al-Assad.
The Arab League has already suspended Syria for failing to implement an Arab peace initiative.
Turkey is not a member of the league, but its foreign minister is to meet his Arab League counterparts during talks in Rabat.
Mr Erdogan says Syria's future cannot be built on "the blood of the oppressed" and says Ankara has abandoned hope that Mr Assad would respond to international demands to stop using violence, the BBC reports.
"Bashar al-Assad should see the tragic ends of the ones who declared war against their own people," Mr Erdogan told MPs of his AK Party. History, he says, will "will mark these leaders as the leaders who feed on blood".
The BBC says Mr Erdogan has become increasingly critical of Syria in recent months.