By Louis Charbonneau and Michelle Nichols
UNITED NATIONS, March 27 (Reuters) - The United Nations said on Tuesday that more than 9,000 civilians have been killed in the Syrian government's yearlong assault on protesters opposed to President Bashar al-Assad, an increase of nearly 1,000 over its previous estimate.
"Violence on the ground has continued unabated, resulting in scores of people killed and injured," Robert Serry, the U.N. special coordinator for the Middle East peace process, told the 15-nation Security Council.
"Credible estimates put the total death toll since the beginning of the uprising one year ago to more than 9,000," he said. "It is urgent to stop the fighting and prevent a further violent escalation of the conflict."
The previous U.N. estimate was that more than 8,000 civilians had been killed.
Serry also referred to U.N.-Arab League envoy Kofi Annan's announcement earlier on Tuesday that the Syrian government had accepted the former U.N. secretary-general's six-point peace plan.
"Immediate steps are needed now from the Syrian government to act on their commitments and demonstrate to the Syrian people that they are ready for a cessation of violence and a political process, issues on which (Annan) will also engage the opposition," Serry said.
Britain's U.N. Ambassador Mark Lyall Grant, president of the Security Council this month, told reporters that the council hoped to receive an update from Annan about Syria's acceptance of the peace plan soon.
"Obviously this is potentially a significant step and we are exploring the possibility of Kofi Annan coming to brief the Security Council later this week or early next week," he said, adding that Annan would likely address the council by video link.
In a rare moment of international unity, Russia and China joined the rest of the U.N. Security Council in throwing its weight behind Annan's efforts to end the conflict and endorsing his six-point peace plan.
Russia and China have twice vetoed resolutions condemning Assad's attempt to crush the opposition with military force but agreed to back last week's council statement in what Western diplomats said was a diplomatic blow to the Syrian government.
Morocco's U.N. Ambassador Mohammed Loulichki, the sole Arab envoy on the council, reacted cautiously to Annan's announcement.
"If Mr. Kofi Annan said that he has received a positive answer we have to see this answer, and I think everybody will assess that," he told reporters.
German Ambassador Peter Wittig was skeptical.
"Syria has a history of credibility gaps," he said. "The Presidential Statement we adopted last week, contains a very clear call on the Syrians to halt the violence, to stop the forward movement, the use of heavy weapons and to start to pull back."
"This we have not seen on the ground," Wittig said.
Assad last year promised U.N. Secretary-General Ban Ki-moon that he would halt military operations against civilian protesters but his security forces continued to crush anti-government demonstrations around the country.