A car bomb has exploded near a mosque north of Damascus, the Syrian capital, as worshippers emerged from prayers, killing at least 30 people, activists have said.

Friday's blast, which struck outside the al-Sahel mosque in the town of Rankous, also wounded dozens of people, according to the UK-based Syrian Observatory for Human Rights.

No further details were immediately available, and it was not clear whether the mosque itself was the target of the attack.

Rankous, which lies about 40km from Damascus, is neither rebel-held nor regime-held. Local residents have an agreement with the rebels not to bring their weapons into the town in order to avoid government shelling.

Activists said that government forces began shelling the same area soon after the explosion occurred, causing at least one more death.

Elsewhere in Damascus province, government troops continued their military campaign on the rebel-held Barzeh district.

Activists said artillery shelling there left several people dead and led to the destruction of some buildings.

Near Damascus International Airport, clashes continued in al-Zamaniya and Shebaa villages between government forces and rebels.

Assad forces are trying to advance further north into the rebel-held eastern Gouta, but have so far been repelled by opposition forces.

Eastern Gouta was one of the towns visited last month by UN inspectors, who then determined that chemical weapons had been used there in a deadly attack on 21 August.

The West accuses Assad's government of carrying out the attack, a claim that Damascus rejects.

UN investigators returned to Syrian this week to investigate at least seven more alleged chemical weapons attacks in the country.

Three of these attacks were reported to have happened after 21 August. The UN said its team of inspectors is set to finish its work by Monday.

A separate team of experts from the Organisation for the Prohibition of Chemical Weapons (OPCW) is due to arrive in Damascus next Tuesday to inspect the country’s chemical arms stockpile.

The OPCW's 41-nation executive council will vote on Friday evening on a on a plan for securing and destroying Syria's stockpile.

If an agreement is sealed at the organisation’s headquarters at The Hague, the UN Security Council in New York can then vote on a UN resolution on Syria's chemical weapons programme.

'US diplomatic failure'

The five permanent members of the deeply divided Security Council had reached agreement on Thursday on a resolution to eliminate Syria's chemical weapons.

The draft agreed upon by Russia, China, the US, France and Britain includes two legally binding demands - that Syria abandons its chemical stockpile and allows unfettered access to the chemical weapons experts.

If Syria fails to comply, the draft says the Security Council would need to adopt a second resolution to impose possible military and other actions on Damascus under Chapter Seven of the UN charter.

Issam Khalil, a member of Assad's ruling Baath party, portrayed the deal as a US diplomatic failure.

"The resolution does not include threats or even possibilities of misinterpretations in a way that would let America and its allies to take advantage of it as they did in Iraq," Khalil said in Damascus.

Nonetheless, after 30 months of paralysis, the agreement represents a breakthrough for the Security Council and rare unity between Russia, which supports Assad's government, and the US, which backs the opposition.

More than 100,000 people have been killed in Syria’s conflict, which started in March 2011 in the form of peaceful protests against the rule of Assad and developed into a civil war.