Syrian army defectors attacked an intelligence complex on the edge of Damascus early on Wednesday, in the first reported assault on a major security facility in the eight-month uprising against President Bashar Al-Assad, activists said.

Members of the Free Syrian Army fired shoulder-mounted rockets and machineguns at a large Air Force Intelligence complex situated on the northern edge of the capital on the Damascus-Aleppo highway at about 2:30 am (0030 GMT).

A gunfight ensued and helicopters circled the area, the sources said.  "I heard several explosions, the sound of machinegun fire being exchanged," said a resident of the suburb of Harasta, who declined to be named.

There was no immediate report of casualties and the area where the fighting occurred remained inaccessible, the sources said.

Syria's ban on most foreign media makes it hard to verify events on the ground.

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 Assad, which the United Nations says has killed 3,500 people.

Syria's military is controlled by Assad's brother Maher and members of their minority Alawite sect, while the army is comprised mostly of Sunni Muslims, who also form the majority of Syria's population and have been defecting from the army in mounting numbers.

The pervasive security apparatus, dominated by Alawites, underpins the power structure. Security chiefs of an estimated eight major secret police organisations answer directly to President Assad. 

An Arab official, who did not want to be named, said insurgent attacks on loyalist forces rose sharply in the last 10 days, although the army remains largely cohesive.

Syrian authorities blame "armed terrorist groups" for the unrest, and say they have killed 1,100 army and police.

Meanwhile, Syria will boycott an Arab League meeting to follow up its decision to suspend Damascus from the organisation.

The meeting of Arab foreign ministers in Rabat on Wednesday comes four days after they decided to discipline Syria for pursuing the crackdown instead of implementing an Arab peace initiative. The League has stopped short of calling for Assad's departure or proposing any Libya-style military intervention.

"In light of statements by officials in Morocco, Syria has decided not to participate in the Arab meeting in Rabat," the agency said, without giving details.

Morocco's foreign minister said "Syrian colleagues" were welcome at the meeting but did not say if Syria's foreign minister could attend. - Reuters