Twin blasts rocked the Syrian capital of Damascus on Friday, leaving at least six people killed as intense clashes and violence continued elsewhere causing a number of casualties.

The first blast had been caused by a booby-trapped motorcycle, which exploded near a mosque on Friday afternoon while worshipers were leaving prayers, the state-news agency SANA said, adding that six members of government forces and civilians had been killed.

A couple of hours later, an explosive device affixed under a car went off in Damascus' district of Mazzeh in front of the courthouse building and the Information Ministry, leaving only six charred and destroyed cars as well as some smashed windows of nearby residential blocs.

The double blasts were coupled with an attack waged by armed insurgent groups at the Hanano barrack in the northern province of Aleppo. The pro-government Addounia TV reported the attack but said the Syrian troops had managed to repel it.

It said several of the assailants had been killed.

Meanwhile, several shells slammed into the streets of the Palestinian camp of Yarmouk in Damascus on Friday, reportedly killing 10 people.

The Syrian state media blamed "armed terrorist groups" for the incident, while the activists held the Syrian troops responsible.

The Yarmouk camp is flanked by two hotspots: the Tadamun area and the Hajar al-Aswad. Both areas have been witnessing armed confrontations between the Syrian army and armed insurgent groups.

Dozens of Palestinian refugees in Syria had been reportedly killed in the chaos that has recently engulfed the capital.

Also Friday, unspecified number of civilians were killed at the Sheikh Maksoud area in northern Aleppo province when armed groups fired mortar shells at the area, the state TV said.

Also in Aleppo, the state-TV said the army unites have carried out a qualitative operation at Bashqatien area, killing big number of armed groups, including groups of the terror-network al-Qaida.

The oppositional Britain-based Syrian Observatory for Human Rights said at least 80 people were killed in Friday's violence nationwide.

The Observatory also reported shelling by government troops and intense clashes in several hotspots nationwide.

Separately, Brigadier Awad Ahmad Ali, chief of the Criminal Security Branch in Damascus, appeared in a televised statement on the Saudi-funded al-Arabiya TV and announced his defection from the regime of Syrian President Bashar al-Assad.

Also, Arab media said Friday that some Syrian diplomats in the Syrian embassy in Malaysia had defected.

Such claims couldn't be confirmed with the absence of official comments.

While the violence on ground is on the rise, Mokhtar Lamani of Canada has been appointed as head of the Office of the Joint Special Representative for Syria in Damascus, Lakhdar Brahimi, according to a UN statement obtained by Xinhua Friday.

The statement said "Mr. Lamani brings a wealth of experience to this role, having held a wide range of diplomatic positions..."

Brahimi, who has been recently appointed as the special joint envoy to Syria, is set to visit Syria within the next couple of weeks to meet with Syrian officials, mainly President Assad, sources said.

Syria said repeatedly that it welcomes Brahimi and pledged that it will cooperate with him in order to draw an end to the 18-month- old crisis.