UN-Arab League envoy Kofi Annan told the Syrian government and rebels on Thursday that the year-long conflict must end at 6am local time on April 12.

Annan told the 193-nation UN General Assembly by video link from Geneva that he was urging "the government and the opposition commanders to issue clear instructions so that the message reaches across the country, down to the fighter and soldier at the local level."

“We must silence the tanks, helicopters, mortars, guns and stop all other forms of violence too — sexual abuse, torture, executions, abductions, destruction of homes, forced displacement and other abuses, including of children.”

Annan addressed the assembly after the 15-nation Security Council increased the pressure on Syria by unanimously adopting a so-called "presidential statement" endorsing next week's deadline and warning Damascus of "further steps" if Syria did not meet the deadline, which the Syrians have publicly accepted.

"The Security Council calls upon the Syrian government to implement urgently and visibly its commitments ... to a) cease troop movements towards population centers, b) cease all use of heavy weapons in such centers, and c) begin pull back of military concentrations in and around population centers," the statement said.

Annan said the Syrian government had told him it had started moving troops out of Idlib, Zabadani and Daraa.

The April 12 deadline was conditioned on the Syrian government beginning its withdrawal from population centers and quartering of its troops on April 10, as pledged by President Bashar al-Assad.

Meanwhile, Syrian troops launched a fierce assault on the Damascus suburb of Douma, described by opposition activists it as "one of the most violent attacks around the capital since the uprising began."

Witnesses told Al-Jazeera that snipers on some 20 buildings were firing at "anything that moved" and residents had endured eight hours of shelling. They said soldiers marched into a main square behind detainees used as human shields.

Such reports have become commonplace in Syria in recent months as Assad has intensified the bloody crackdown on the more than a year long popular uprising against his 11 year autocratic rule.

The Syrian Observatory for Human Rights told AFP that at least 33 people, including 14 soldiers,were killed yesterday, 16 of them in the city of Homs and 14 in Idlib province.

At least 92 were killed across Syria on Wednesday in assaults launched by Assad's forces. Reports also circulated Wednesday that Syrian troops were firebombing the homes of opposition activists and suspected rebel fighters across the country.

Amid the violence, a team led by Norwegian Maj. Gen. Robert Mood arrived in Damascus on Wednesday to negotiate the possible deployment of a UN team tasked with monitoring the ceasefire agreement between Syrian government troops and rebel forces.

The UN is already asking member nations to contribute about 200 to 250 soldiers who would monitor a ceasefire, should it come into effect.