Syrian president Bashar al-Assad accepted a peace plan brokered by Mr Annan on Thursday, but the bloodshed has continued.
“The government must stop first and then discuss a cessation of hostilities with the other side,” Mr Annan’s spokesman said. “We are appealing to the stronger party to make a gesture of good faith… The deadline is now.”
Yesterday, activists reported clashes in suburbs of the Syrian capital, in northern Idlib province, the central province of Homs and eastern Syria.
The Local Co-ordination Committees said 15 people were killed, including eight in the town of Quriya in the eastern Deir el-Zour province, where, security forces opened fire to disperse protesters, triggering clashes with local rebels.
In Damascus, troops opened fire on protesters in the Kafar Souseh district, killing at least one person.
US secretary of state Hillary Clinton, meanwhile, was in Saudi Arabia for talks with King Abdullah in an effort to develop a strategy on the Syria crisis.
The visit comes ahead of a 60-nation gathering of the “Friends of the Syrian People” in Istanbul aimed at finding ways to aid Syria’s fractured opposition.
Mr Annan’s plan calls for an immediate, two-hour halt in fighting every day to allow aid in and the wounded out. The plan also outlines an eventual ceasefire, which requires government forces to withdraw from towns and cities and rebels to stop their attacks, allowing a UN monitoring mission to be established.