U.N.-Arab League envoy Kofi Annan says the Syrian government must immediately implement a cease-fire and stop its attacks on opposition groups, as fresh clashes broke out across the country on Friday.

Mr. Annan's spokesperson told reporters in Geneva that the “deadline is now” for President Bashar al-Assad to implement the six-point peace plan drawn up by the former U.N. chief. He did not specify what action, if any, would be taken if Mr. Assad did not comply.

Arab leaders at a Baghdad summit on Thursday endorsed the Syria peace plan and called for its immediate implementation.

Mr. Assad agreed to the peace plan on Tuesday but government forces have not shown restraint.

Chatham House Middle East analyst Nadim Shehadi says Mr. Assad may have agreed to the peace plan as a stalling tactic.

“It's something that the regime can use to buy time and the regime can always blame the violence on others and the nonimplementation on others and can always buy time by slowly implementing or seeming to implement but not really implementing.”

Rights groups say at least 11 people were killed on Friday in clashes between demonstrators and security forces. The groups say the violence erupted as anti-government protests took place in several cities.

Meanwhile, U.S. Secretary of State Hillary Clinton met with Saudi Arabia's King Abdullah and other officials in Riyadh on Friday in a bid to increase pressure on Mr. Assad to stop his year-long crackdown on dissent.

On Saturday, Clinton will attend a meeting of regional Gulf diplomats. Clinton will travel to Turkey on Sunday for the second session of the so-called “Friends of Syria” meeting, which will be attended by dozens of nations who support Syrian rebel groups.

The meeting is expected to focus on how to ensure President Assad complies with the peace plan, which calls for a cease-fire, a daily two-hour humanitarian truce, and political dialogue to end the conflict.

Analyst Shehadi says this week's flurry of diplomatic activity may not indicate progress towards a resolution.

“Sometimes one sees a lot of diplomatic activity when people do not know what to do when there is a crisis and there is no clear policy.”

The U.S. tightened economic pressure Friday on Damascus by imposing sanctions on Defense Minister Dawood Rajiha and two other security officials.

The United Nations says violence linked to Syria's crackdown on the revolt has killed more than 9,000 people.