The UN's top human rights official said today that there should be no amnesty for serious crimes committed in Syria, even if the threat of prosecution might motivate members of the regime to cling to power at all costs.

A fragile ceasefire brokered by the UN took hold in Syria today with regime forces apparently halting widespread attacks on the opposition but still defying demands by international envoy Kofi Annan to pull troops back to barracks.

Syrian rebels say they are making a “tactical retreat” from the besieged district of Baba Amr in Homs because of worsening humanitarian conditions.

Western and Arab countries responded with outrage yesterday after Russia and China vetoed a UN Security Council resolution that would have backed an Arab plan urging Syrian President Bashar al-Assad to give up power.

Syria’s opposition appealed for international backing today, a day after Russia and China vetoed a UN Security Council resolution aimed at pressuring President Bashar Assad to end his bloody crackdown on an uprising that has raged for almost 11 months.

At least 14 people were killed today when a string of explosions struck a police truck transporting prisoners in a tense area of north-western Syria, the country's state-run news agency and an opposition group said.

Syria's two largest opposition groups have signed an agreement on setting up a democracy after President Bashar Assad's regime falls, opposition figures said today.

Syrian opposition activists say the army has begun withdrawing tanks from the restive city of Homs after days of assaults and just as an Arab League observer mission arrives in the country.

SYRIAN security forces killed 10 people in Homs yesterday, activists said, and there was no sign yet of troops leaving cities under an Arab League agreement to end bloodshed after seven months of protests against President Bashar al-Assad.

Acil Tabbara reports from Dubai on unrest in the region and the role played by Facebook