U.N.-Arab League envoy Kofi Annan says he is “encouraged” by reports that a shaky cease-fire between government troops and rebels in Syria seems to be holding, despite scattered violence.

In a briefing to the United Nations Security Council Thursday, Mr. Annan urged Damascus to take further steps by removing troops and heavy weapons from major population centers. Diplomats say Mr. Annan also told the council that Syria had not fully complied with the terms of the peace plan that he brokered in March.

But Syria's envoy to the U.N. said his government had ended attacks and expects opposition militias to do the same. Ambassador Bashar Ja'afari said “the moment of truth has come.”

Ja'afari blamed anti-government forces for several violent acts that he said occurred after the cease-fire deadline.

Russian Ambassador Vitaly Churkin said Moscow is encouraged by the truce, but that all parties need to show “maximum prudence” for it to hold. He expressed hope that by Friday, the U.N. Security Council will adopt the resolution required to authorize the unarmed observers to monitor the cease-fire.

Chinese Ambassador Li Baodong called on all parties to fulfill their international commitments. He expressed Beijing's support for Mr. Annan's peace plans and his request for a monitoring mission in Syria.

But rights activists said Syrian forces killed at least three civilians after the cease-fire deadline passed. They said the attacks took place in areas including the protest hubs of Homs and Hama and that the Syrian troops remain deployed in those areas and are on high alert.

U.S. President Barack Obama and French President Nicolas Sarkozy issued a joint statement urging Syria to abide by Mr. Annan's plan.

White House Press Secretary Jay Carney said that although Syrian troops have appeared to stop widespread attacks on the opposition, incidents of violence were reported, and Damascus rebuffed demands to return troops to their barracks. Carney said this was “unacceptable,” adding that the message to the Assad government is to stop the violence and stop killing its people.

U.S. Secretary of State Hillary Clinton said Syrian President Bashar al-Assad cannot “pick and choose” which parts of the agreements he wants to accept. She said Washington supports sending a U.N. monitoring mission to Syria.

U.N. chief Ban Ki-moon said the international community must be united if it is going to keep Syria from descending into “chaos.” Mr. Ban said plans were under way to send observers to Syria. Diplomats said the first U.N. peacekeepers could be dispatched as early as Friday.