Syrian forces bombarded districts of the city of Homs on Saturday in their drive to crush a revolt against President Bashar al-Assad, whose ally Russia said it would not support an Arab peace plan circulating at the United Nations.

Activists said 11 people were killed in the latest attacks in a week-long government siege of Homs, Syria's third largest city, which has been at the heart of an uprising that broke out 11 months ago.

Tens of shabbiha (Alawite militiamen loyal to Assad) along with army snipers and two tanks have deployed at the citadel and they are bombarding Old Homs with mortar rounds and anti-aircraft guns, activist Malek Mohammad said by satellite phone from the city, 140 km (88 miles) north of Damascus.

Mohammed Hassan, another opposition campaigner in Homs, told Reuters by telephone that a 55-year-old woman was among those killed by shellfire on the Bab Amro district.

Assad has dispatched loyal forces into cites and towns across Syria to put down the uprising, drawing armed resistance, defections by soldiers from the Sunni Muslim majority, and international outrage at a crackdown that has killed thousands of civilians.

In a rare sign of compromise, Assad's forces entered the besieged town of Zabadani in the mountains near the border with Lebanon after agreeing a ceasefire with rebels, according to Kamal al-Labwani, an opposition leader in exile.

Under the agreement, reached after a week-long tank and artillery bombardment that killed at least 100 in the town of 20,000, rebel forces will be allowed to pull out if they give up weapons and armour seized from government forces, Labwani said.

AVOIDING A BLOODBATH

Cooler heads in the military somehow prevailed over whoever has been issuing orders to shell Zabadani with heavy artillery. In the end it was in the interest of the two sides to prevent a bloodbath, Labwani said.

The Syrian Observatory for Human Rights reported that three people had been killed in the bombardment on Saturday.

On Friday, bombings targeting security forces killed at least 28 people in Syria's second city of Aleppo, so far on the sidelines of the uprising.

Assad has ignored repeated international appeals, the latest from the European Union, to halt his crackdown.

However, the world remains divided over how to end the conflict. A week ago, Russia and China vetoed a U.N. Security Council resolution sponsored by Western and Arab states that backed an Arab League call for Assad to step down.

Saudi Arabia has circulated a similar draft for the U.N. General Assembly, where there is no power of veto.

But Russian Deputy Foreign Minister Gennady Gatilov said on Saturday that Moscow could not support a move resting on the same unbalanced draft resolution text.

The dispute brings no relief to Homs, where activists say the government offensive on mostly Sunni Muslim rebel-held areas has killed at least 300 people in the past week.

Food and medical supplies were running low in blockaded areas and many people were trapped in their homes.

SHRAPNEL

YouTube footage provided by activists showed a doctor at a field hospital next to the body of the woman of 55 reportedly killed on Saturday. Shrapnel hit her in the head and completely drained her brain matter, he says.

Accounts could not be independently confirmed as Syria restricts access by most foreign journalists.

The 46-year-old Assad belongs to the Alawite sect, an offshoot of Shi'ite Islam that has dominated the majority Sunni country since his late father took control in a 1970 coup.

Security forces have made house-to-house raids in Homs in the last two days. The bodies of three people shot by snipers were pulled from the streets on Saturday, activists said.

YouTube footage from Friday showed two tanks said to be on the edge of Bab Amro, one firing its main gun across a highway.

The indiscriminate shelling is killing mostly civilians, said Fawaz Tello, of the opposition Syrian National Council, arguing that Assad wanted to avoid pushing his troops into street fighting and was banking on the bombardment to force rebel fighters to withdraw.

In Damascus, gunmen shot dead a senior Syrian military doctor outside his home in northern Damascus on Saturday, the state news agency SANA said.

It blamed an armed terrorist group for the assassination of Brigadier-General Issa al-Khouli, whom it described as a doctor and hospital director. He was the most senior figure to have been reported killed in Damascus.

His killing followed a four-hour clash in the capital on Friday night pitting Free Syrian Army rebels against troops backed by armoured vehicles who had entered the neighbourhood of

al-Qaboun, activists said. ID:nL5E8DACME]

AMBUSH

The British-based Observatory said 10 soldiers had been killed in an ambush by army defectors using roadside bombs and hand grenades on Friday in the rebellious Idlib region.

In Douma, south of Damascus, an officer and eight soldiers defected along with a tank after clashes between army deserters and security forces, it said.

Opposition to Assad has evolved from pro-democracy street protests to armed insurrection over the past 11 months. World powers fear a slide into civil war with knock-on effects for Syria's neighbours - Turkey, Iraq, Jordan, Israel and Lebanon.

Gulf Arab states, the United States, Europe and Turkey hope diplomacy can force Assad out and have ruled out military action of the kind that helped oust Libya's Muammar Gaddafi last year.

Assad can count on the support of Russia, Syria's main arms supplier and an ally stretching back to the Soviet era, as well as Iran. Moscow, which is keen to counter U.S. influence in the Middle East, insists foreign powers should not interfere.

The U.N. assembly is due to discuss Syria on Monday and vote

later in the week on the draft resolution, which fully supports an Arab League plan floated last month.

The Arab League was to meet in Cairo on Sunday to discuss the idea of a joint Arab-U.N. monitoring mission for Syria.

Ayham Kamel, an analyst at Eurasia Group, said the Russian and Chinese vetoes showed that change in Syria was not imminent. As rebel forces lacked structure and a unified command, Assad would keep the military edge but find it hard to crush the revolt.

In the next few months, Syria will transition from civil conflict into civil war. Assad's power and control over the country will diminish and civilian casualties on both sides are expected to rise, Kamel said.

Highlighting the danger of the conflict spilling over borders, supporters and opponents of Assad fought in the streets of Lebanon's northern city of Tripoli on Saturday, a security source said. Two people were killed and eight wounded, some of them soldiers who had been deployed to halt the fighting.

(Additional reporting by Patrick Worsnip at the United Nations and Gleb Bryanski in Moscow; Writing by Angus MacSwan in Beirut; Editing by Alistair Lyon)