A cease-fire in Syria showed more signs of unraveling on Friday, as security forces fired shots at protesters and pounded opposition strongholds while the government blamed rebels for a deadly explosion.

Activists say thousands of protesters calling for President Bashar al-Assad's departure demonstrated across Syria under a heavy security force presence in some areas.

Rights groups say Syrian forces killed at least 11 civilians, including several in the flashpoint Homs region.

Hivin Kako, of the Syrian Observatory for Human Rights, told VOA of government shelling in Homs.

“There has been mortar used since the early hours of the morning — this is regarding what is happening in Homs in different area[s]. There has been bombardment by the Syrian regular forces.”

State-run media reports say at least 18 security force members have been killed in a series of attacks across Syria, including 10 in an explosion near the Golan Heights region. The government blamed “armed terrorists” for most of the attacks.

As the violence unfolded, diplomatic attempts continued aimed at enforcing provisions in a peace agreement brokered last week by international envoy Kofi Annan.

U.N. Security Council diplomats circulated draft resolutions on Friday that would boost the number of international monitors in Syria from about 30 to 300.

A spokesman for Mr. Annan described the cease-fire as “very fragile” on Friday. He expressed hope that additional monitors would be in place in Syria very soon.

Kako said the Annan peace plan is Syria's last hope.

“This is the last chance to save the country and to move forward towards democracy and a transitional period in a peaceful way. Otherwise, the country will be dragged into a war.”

European diplomats said Friday that a fresh round of EU sanctions against Damascus could be adopted as early as Monday.

French Foreign Minister Alain Juppe said Friday the world cannot afford to wait much longer for the cease-fire and peace plan that Mr. Annan put forward to take hold, warning Syria is on the verge of descending into civil war.

China, which has blocked stronger U.N. action against the Syrian regime, said it was ready to do more to help uphold the truce – saying it is willing to contribute observers to the U.N. mission.

The United Nations estimates that Syria's crackdown on the revolt has killed more than 9,000 people.