Regime forces resumed their assault on the Syrian protest city of Homs on Monday, activists said, after Damascus rejected an Arab plan to send a peacekeeping force to the unrest-hit country.

Shortly before sunrise, the army launched mortars into Baba Amr, a rebel stronghold in the central city, as forces swept through southern Daraa province arresting dissidents, said the Syrian Observatory for Human Rights.

"The neighbourhood of Baba Amr has been subjected to sporadic shelling since 5:00 am (0300 GMT) by the Syrian army," the Britain-based Observatory said in a statement.

"Forces launched an assault and are arresting people in Sasra al-Sham after an explosion in Dael, in Daraa province," cradle of the 11-month uprising against President Bashar al-Assad.

"There were fierce clashes between defectors and the army which stormed Lajat and arrested the mothers of four dissidents," it said, adding a sniper killed a civilian in the central city of Hama.

Rights groups say Assad's forces have killed at least 500 people in Homs since they began attacking the central city with a barrage or tank shells, mortars and rocket-propelled grenades on February 4.

After marathon talks in Cairo on Sunday, the Arab League said it had agreed to open contacts with Syria's opposition and ask the United Nations to form a joint peacekeeping force to the nation.

Arab League diplomats "will open channels of communication with the Syrian opposition and offer full political and financial support, urging (the opposition) to unify its ranks," said a League statement.

They would also 'ask the UN Security Council to issue a decision on the formation of a joint UN-Arab peacekeeping force to oversee the implementation of a ceasefire.'

The 22-member bloc announced an end to its own observer mission to Syria, suspended last month amid an upsurge in violence.

Syria's ambassador to Cairo denounced the resolution, which only Algeria and Lebanon expressed reservations about.

"The Syrian Arab Republic categorically rejects the decisions of the Arab League," which 'reflects the hysteria of these governments' after failing to get foreign intervention at the UN Security Council, said Yusef Ahmed.

Al-Watan newspaper, which is close to Syria's government, on Monday slammed Arab nations for backing the latest peace initiative, singling out Qatar.

"The Arabs have exhausted all avenues and all they can do now is bring in foreign forces to occupy Syria," it said.

"Qatar's leaders are behaving like megalomaniacs. They promised to spend hundreds of billions of dollars to bring down the Syrian regime."

The government daily Ath-Thawra said the League meeting 'marked the peak of political and moral rudeness, which was at its lowest.'

"The Arab League countries were trying to outbid each other as far scheming, betrayal and political prostitution."

Burhan Ghalioun, leader of the opposition Syrian National Council, welcomed the moves as 'a first step' towards the fall of the regime.

As the military pressed its onslaught on Homs, refugees who had fled the city across the border to Lebanon told of the horrors they had witnessed.

"The army of Bashar al-Assad destroyed our homes," Abu Ibrahim said.

"Before, we were bombarded by mortars or rocket-propelled grenades, but now they are using tanks and helicopters," he said, adding his 10-year-old daughter has refused food since seeing dead bodies in the beleaguered city.

The Syrian Arab Red Crescent and International Committee of the Red Cross said their 'volunteers are distributing food, medical supplies, blankets, and hygiene consumables to thousands of people' in Homs.

"The population, particularly the wounded and sick, are bearing the brunt of the violence," the ICRC's Marianne Gasser said in a statement.

Arab and western states will launch a bid at the UN General Assembly this week to put pressure on Assad after Saudi Arabia and Qatar drew up a resolution backing the League plan to end the crackdown.

The move follows the Russian and Chinese veto of virtually the same resolution in the Security Council eight days ago. Moscow and Beijing are expected to oppose the new text.

However, no one can veto resolutions in the 193-nation General Assembly, which carry less weight.

The United States and its allies are bringing 'pressure to bear' on Syria, White House chief of Staff Jacob Lew said.

On Sunday, state television showed an official funeral for the 28 people authorities say were killed two days earlier in twin car bombs in the northern city of Aleppo.

The government blamed the attacks on foreign-backed 'terrorists,' but the rebel Free Syrian Army had accused the regime of carrying out the bombings to divert attention away from its brutal offensives elsewhere.

A US media report citing unnamed American officials said Al-Qaeda's Iraqi branch was likely to have carried out the bombings, along with attacks in Damascus in December and January.

Rights groups say more than 6,000 people have died since protests began in Syria in March last year, inspired by similar movements in Tunisia, Egypt and Libya.