The U.N.'s human rights chief called Friday for Syria to be referred to the International Criminal Court over allegations that its crackdown on opposition protesters has led to crimes against humanity.

Navi Pillay, the U.N. High Commissioner for Human Rights, said fresh reports from the country — including that 307 children have been killed since March — reinforced the need for the Security Council to submit the situation in Syria to the Hague-based court.

Mutinous soldiers have attacked a Syrian air force intelligence base in the northwestern province of Idlib, killing eight people, a rights group said on Friday.

"A group of deserters attacked an air force intelligence center... killing eight people from the base," the Syrian Observatory for Human Rights said in a statement received in Nicosia.

U.S. Vice President Joe Biden urged Syria's Bashar Assad to quit, in a Turkish newspaper interview published Friday, adding to growing global pressure on the regime over its crackdown on dissidents.

"The United States' position on Syria is clear. The Syrian regime must end its brutality against its own people and President Assad must step down so a peaceful transition that respects the will of the people can take place," Biden told the Hurriyet daily.

French authorities have increased security for Syrian opposition members based in France who have come under threat, the interior minister said Friday.

Claude Gueant did not specify the nature of the threats or of the new security measures.

A Syrian government run by the country's main opposition group would cut ties to Iran, and end arms supplies to Hizbullah and Hamas, the group's leader told the Wall Street Journal published Friday.

The interview with Burhan Ghalioun, president of the Syrian National Council, came eight months into an increasingly violent uprising against Syrian President Bashar Assad, with rebels seeking international support.

Washington on Thursday placed economic sanctions on a senior Syrian general and a financier uncle of President Bashar al-Assad, adding new pressure on the regime over its bloody political crackdown.

The Treasury Department added Mohammed Makhlouf, Assad's maternal uncle and the father of already-sanctioned telecoms magnate Rami Makhlouf, and 4th armored division General Aus Aslan, to its growing list of Syrian figures and organizations that Americans are banned from doing business with.

Syria has suspended its participation in the Mediterranean Union in retaliation for punitive measures against its regime by European states, state media said on Thursday.

"Syria is suspending its membership in the Mediterranean Union in response to European measures taken against it," said a statement carried by the official SANA news agency.

The number of people killed in Syria following a crackdown on protesters since March has reached at least 4,000, the U.N. rights chief said on Thursday, as the European Union tightened sanctions against Syria's energy and financial sectors.

"We are placing the figure at 4,000. But the information coming to us is that it's much more," said United Nations High Commissioner for Human Rights Navi Pillay during a conference in Geneva.

Kuwait on Thursday appealed to its nationals to leave Syria and refrain from travelling there because of safety concerns amid a deadly eight-month crackdown on democracy protests.

"The foreign ministry calls on citizens currently present in Syria to leave for their own safety," it said in a statement quoted by the state-run KUNA news agency.

Syria's civilian opposition and army rebels have agreed to coordinate their struggle against President Bashar Assad's regime, an official said Thursday.

The first meeting between the Syrian National Council and the Free Syrian Army earlier this week in Turkey appeared to mark a change of tack from the SNC's previous reluctance to back the armed struggle.