An Arab League proposal to boost support for the uprising against Syrian President Bashar al-Assad and to send in foreign peacekeepers drew a guarded international response on Monday and showed little sign of halting the bloodshed soon.

Russia, Assad's close ally and main arms supplier, said it could not support a peacekeeping mission unless both sides ceased the violence first.

Some felt the moves might only fan the flames of war.

We feel the decisions are taking a grave turn for Syria and for the region, Lebanon's Foreign Minister Adnan Mansour said in Beirut.

Other observers said it was just the start of a long and complex process to resolve what is potentially the most dangerous of the Arab Spring revolts.

On the battlefront, Syrian government forces bombarded rebellious districts of Homs and attacked other cities in their campaign to crush opposition to Assad's 11-year rule.

Mortar rounds and tank fire pounded Baba Amro district but casualties could not be tallied because communication were cut off, activist Mohammad al-Hassan told Reuters from Homs.

Activists said 23 people were killed on Sunday, adding to a toll of more than 300 since the assault on Homs, strategically located on the highway between the capital Damascus and second city Aleppo, began on February 3.

World powers meanwhile digested Arab League proposals from a meeting in Cairo on Sunday which called for a joint United Nations-Arab peacekeeping force for Syria and pledged to provide political and material aid to the opposition.

The plan faced all kinds of obstacles. Foreign governments are divided over how to resolve the crisis and Russia and China already vetoed a U.N. Security Council resolution on Syria on February 4. which called for Assad to step down.

In Moscow, Foreign Minister Sergei Lavrov made clear Russia would not support the peacekeeping plan unless there was a halt to violence by both government forces and their armed opponents. He suggested the latter would be tough to achieve.

U.N. peace missions need to first have a peace to support, Lavrov told a news conference.

The tragedy is that the armed groups that are confronting the forces of the regime are not subordinate to anyone and are not under control, Lavrov said, adding that the opposition had modern guns, mortars and grenade launchers and also sow death.

A halt to the violence must be universal, he said.

China backed what it termed the Arab League's mediation but offered no clear sign of support for the peacekeeper call.

Relevant moves by the United Nations should be conducive towards lessening tension in Syria...rather than complicating things, Chinese Foreign Ministry spokesman Liu Weimin said.

The United States and Europe are reluctant to get dragged in militarily, fearing that given Syria's position in the Middle East's religious, ethnic and political faultlines, this would be more risky and complicated than the NATO-led air support that helped Libyan rebels oust Muammar Gaddafi last year.

British Foreign Secretary William Hague reflected that caution, saying any peacekeeping troops in Syria should come from non-Western countries.

I don't see the way forward in Syria as being Western boots on the ground in any form, including in any peacekeeping form, he told reporters on a visit to South Africa.

France was unenthusiastic about sending in foreign troops.

We think that any external military intervention would only make the situation worse ..., French Foreign Minister Alain Juppe said.

A peacekeeping mission would in any case require the cooperation of Syria, which dismissed the League's resolution as a hostile act that targets Syria's security and stability.

The fragmented nature of the opposition to Assad, who is from the Alawite minority in the mostly Sunni Muslim country, is also a problem for those keen on political change in Syria.

The Arab League effort also highlighted regional rivalries. Its moves have been driven by Saudi Arabia and other Sunni-ruled Gulf monarchies who have long resented Assad's close ties to Shi'ite regional rival Iran.

Beirut-based political commentator Rami Khouri said that although the Arab plan was fraught with difficulty, it was also incredibly bold and incredibly daring.

It is the beginning of a very complex process driven by the Arab League, he told Reuters.

It hinged on convincing Russia that it must eventually give up its support for Assad and bringing the opposition together.

Asked if the conflict might get bloodier in the short-term, Khouri said: It can't get much worse than it is, and this will continue.

Other analysts believe Syria is slipping towards a civil war whose sectarian dimensions could inflame the wider region.

But Assad's downfall is far from imminent. The unrelenting assaults on opposition strongholds show his determination to crush his foes and resist reforms other than on his own terms, they say.

OVERNIGHT SHELLING

In Homs, government troops concentrated their fire on Baba Amro in the south and al-Waer in the west, which borders the Military College, a main assembly point for tanks and government troops, opposition campaigners said.

Activist Hassan said al-Waer, scene of large pro-democracy demonstrations for months, had come under attack in the last several days from pro-Assad militia known as shabbiha.

We heard that the Free Syrian Army has started responding by attacking roadblocks being manned by shabbiha. Communications with al-Waer have been cut off and the sound of shelling can be now heard, Hassan said.

The Free Syrian Army, led by military defectors, has taken the central role in armed opposition to the Assad government. Accounts of action on the ground are difficult to verify because Syria restricts access by journalists.

On Sunday armour-backed troops raided the al-Inshaat district of Homs. Tanks ran over civilian cars and troops ransacked houses and burned furniture in the streets as collective punishment, the Coalition of Free Homs said.

The Syrian Observatory for Human Rights said shelling had also started up again on the city of Rastan in Homs province.

Government forces had made failed attempts to storm Rastan at dawn from its southern entrance. Rebels destroyed an armoured vehicle and killed three soldiers, the Observatory said.

In the city of Hama, 50 km (30 miles) north of Homs, government forces backed by tanks and armoured vehicles killed at least one man when they raided neighbourhoods on Sunday near the countryside where the Free Syrian Army has been active.

It is the third day of such incursions. They fire heavy machineguns and anti-aircraft guns at random, then they go in and raid houses and arrest dozens of people, activist Fady al-Jaber said from Hama.

(Additional reporting by Ben Blanchard in Beijing, Steve Gutterman in Moscow and Erika Solomon in Beirut; Writing by Angus MacSwan; Editing by Giles Elgood)