Syrian forces unleashed their heaviest pounding of Homs in two weeks on Friday, activists said after the UN General Assembly overwhelmingly backed an Arab initiative calling on President Bashar al-Assad to stand down.

Rockets crashed into Khaldiyeh and Bayyada, strongholds of resistance in the central protest hub, at the rate of four a minute, according to one opposition activist inside the beleaguered city.

"It's the most violent in 14 days. It's unbelievable -- extreme violence the like of which we have never seen before, with an average of four rockets every minute," said Hadi Abdullah of the General Commission of the Syrian Revolution.

"There are thousands of people isolated in Homs... There are neighbourhoods that we know nothing about. I myself do not know if my parents are okay. I have had no news from them for 14 days," he told AFP by phone.

Footage of the assault showed a tank firing on Homs, according to a video activists uploaded to YouTube.

Nine bodies of unidentified people were found on Friday morning in Homs, said the Syrian Observatory for Human Rights, which also reported the shelling was the most intense in a fortnight.

Two people died Friday in eastern Deir Ezzor province, one a young man gunned down by security forces manning a checkpoint and the other a soldier, said the Britain-based monitors.

The violence comes after the UN General Assembly on Thursday demanded an immediate halt to Syria's brutal crackdown on dissent, which human rights groups say has cost more than 6,000 lives in the past 11 months.

In a strongly worded resolution adopted by a 137-12 vote, UN member states demanded Assad's government stop attacking civilian demonstrators and start pulling troops back to barracks.

The resolution calls on Damascus "to stop all violence or reprisals immediately, in accordance with the League of Arab States initiative."

It was referring to a peace plan put forward by the pan-Arab bloc calling on Assad to hand power over to his deputy and for the formation of a unity government ahead of elections.

Russia, China and Iran opposed the non-binding resolution put forward by Arab states with Western support just days after Beijing and Moscow vetoed a similar resolution at the UN Security Council.

Such a strong vote in favour of the resolution adds to mounting pressure on Assad to curb a crackdown that left at least 41 people dead on Thursday as security forces bore down on focal points of dissent.

Egypt's deputy UN ambassador, Osama Abdelkhalek, said the General Assembly had sent an "unambiguous message" to Damascus: "It is high time to listen to the voice of the people."

But Syrian envoy Bashar Jaafari lashed out at other Arab nations, saying Western powers had exploited the Arab League to "internationalise" the crisis.

"The Arab Trojan horse has been unmasked today," he said.

Iran's UN representative, Mohammad Khazaee, warned the resolution would only deepen the crisis, "with all its ramifications to the region as a whole."

A Chinese envoy on Friday begins a two-day visit to Damascus in a new push for peace. On the eve of his trip, Vice Foreign Minister Zhai Jun said Beijing opposed armed intervention and forced "regime change" in Syria.

Amnesty International said the UN resolution "sends a clear and unequivocal message from the international community to Syria to immediately end the brutal assault against innocent people."

Meanwhile, a human rights lawyer said blogger Razan Ghazzawi, a figurehead of the uprising, had been arrested, along with leading rights activist Mazen Darwish, his wife and 11 others.

"We at the Syrian Centre for Legal Studies condemn these arrests and call on Syrian authorities to immediately release them," the lawyer, Anwar Bunni, said in a statement echoed by Paris-based media watchdog Reporters Without Borders.

On Thursday, Syria's opposition rejected a newly drafted constitution that could end nearly five decades of single-party rule, and urged voters to boycott a February 26 referendum on the charter.

One of them, the Local Coordination Committees, also called for stepped-up efforts to oust Assad.

"The draft constitution is no more than a political tool or a policy paper written by the barbaric regime," it said. "We see no alternative but to topple the regime."

The National Coordination Committee for Democratic Change, another opposition group, said it also planned to boycott the vote.

"It is impossible for us to take part in this referendum before a stop to the violence and killings," its leader Hassan Abdel Azim told AFP.

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