* Annan sets precise cease-fire deadline for April 12
* Syrian U.N. ambassador says police will remain
* Syria's army withdrawal claim disputed by opposition
* Refugee flow to Turkey accelerates
BEIRUT/UNITED NATIONS, April 5 U.N. Secretary-General Ban Ki-moon said Thursday that Syria's conflict is deepening and attacks on civilian areas show no sign of abating, despite assurances from Damascus that it has begun withdrawing troops under an international peace plan.
Residents of at least one area under fire from the forces of President Bashar al-Assad poured scorn on the official assertions that troops were pulling back in several cities before a cease-fire which is supposed to start on April 10.
International envoy Kofi Annan, whose plan aims to end a year of bloodshed during the uprising against Assad, said that "more far-reaching action is urgently required" to silence the tanks and halt all forms of violence.
Addressing the United Nations Security Council, Ban gave a pessimistic assessment of the situation in Syria.
"Despite the Syrian government's acceptance of the joint special envoy's plan of initial proposals to resolve the crisis, the violence and assaults in civilian areas have not stopped. The situation on the ground continues to deteriorate," Ban said.
The United Nations says Assad's forces have killed more than 9,000 people in the conflict, which began with peaceful protests although armed rebels later began fighting back. Syria told the world body this week that 6,044 people had died, including 2,566 soldiers and police.
The Security Council agreed Thursday to a statement urging Syria to meet Annan's deadline.
Annan, a joint envoy of the U.N. and Arab League, said both the government and opposition must stop fighting at 6 a.m. Syrian time on April 12, if Damascus meets its deadline 48 hours earlier to pull back troops from cities and cease heavy weapons use in populated areas.
"I urge 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," Annan told the U.N. General Assembly by video link from Geneva.
"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 on children," he said.
ACTION URGENTLY REQUIRED
Annan, a former U.N. chief, said Damascus had told him troop withdrawals were under way, but he said more needed to be done.
"The government has informed me of partial withdrawals from three locations - Idlib, Zabadani, and Deraa. I await further action and fuller information," he said.
"The government has indicated that it will continue to update me on steps it is taking. But it is clear that more far-reaching action is urgently required."
Syrian U.N. Ambassador Bashar Ja'afari, however, hinted at a possible loophole in Annan's peace plan, which does not refer to the withdrawal of police forces. He told reporters the police were not covered by the Tuesday deadline for Syrian troop pullbacks because "the deployment of the police is to protect the civilians."
Opposition activists say the army and police have been responsible for killing civilians in the government's yearlong attempt to stamp out pro-democracy demonstrations.
One Zabadani resident said no significant withdrawal was under way. "They are complete liars, there is no army withdrawal, they are still in the middle of the city. They fired on the city this morning, like they do every day," a man calling himself Abu Mustafa said by telephone from Zabadani near the Lebanon border.
"The army withdrew 15 tanks yesterday, but the rest are all around the checkpoints as usual," Abu Mustafa said.
The opposition Syrian Observatory for Human Rights reported that at least 33 people, including 14 soldiers, were killed on Thursday, 16 of them in the city of Homs and 14 in Idlib province.
Video taken by activists just outside Aleppo, Syria's second city, showed five tanks and armored personnel carriers firing heavy machine guns as they advanced through a village.
A diplomatic face-off intensified between Syria's ally Russia and Western powers who want Assad to go. France accused the 46-year-old Syrian leader of not fulfilling his promises, while Moscow told opposition supporters abroad not to set ultimatums.
More than 42,000 Syrians have fled the country since the uprising began. Turkey said more than 1,600 had crossed the border in the last two days, twice the recent average rate.
Blasts and gunfire rocked Douma and activists said army reinforcements headed for the town near Damascus shortly before a senior U.N. peacekeeping official arrived in the capital.
Norwegian Army former Chief of Staff Major-General Robert Mood brought an advance planning team of 10 to decide how around 250 U.N. monitors might oversee the truce between army and insurgents if it takes effect by next Thursday.
Some analysts say any arrival of men in U.N. blue helmets will embolden a return to mass protests, as happened when an Arab League monitoring mission began operating in Syria in December. It was later withdrawn as violence increased.
Mood has experience of armed U.N. peacekeeping operations in Kosovo, where around 60,000 troops were deployed in 1999 after a cease-fire and army withdrawal agreement were already in place.
In Syria, where Western powers have ruled out military intervention, Annan envisages only unarmed U.N. monitors.
QUEST FOR CONTRIBUTORS
U.N. member states were already being asked to provide troops for the mission, Annan's spokesman said. Annan will hold talks on Syria in Iran, Assad's main regional ally, on April 11, he added.
Annan has assiduously sought backing from Assad's friends as well as his foes for his difficult peace mission.
Russia said it could support the new Security Council statement backing Annan's timeline for a cease-fire if it does not level "threats and ultimatums" against Assad.
"The Syrian government has accepted (Annan's) proposals and has begun implementing them, and it is very important not to undermine this process with ultimatums and threats," Russian Foreign Minister Sergei Lavrov said Thursday.
Syria's state news agency quoted Lavrov as telling Annan by telephone that "not only the Syrian authorities, but also the opposition" must take steps to implement the envoy's peace plan.
Russia has taken a pro-Assad tone, but some diplomats say Moscow has grown increasingly frustrated with Damascus and its failure to end the uprising, even as it denounces Western, Arab and Turkish calls for the Syrian leader to quit.