Syrian forces killed another 24 people in flashpoint cities on Friday, rights activists said, as the opposition warned of an impending "massacre" by regime troops ringing the central protest hub Homs.
The United States and Britain separately voiced concern over the bloodletting in Homs, where 11 of Friday's deaths occurred, and Washington urged President Bashar al-Assad's regime to allow independent monitors into the country in line with an Arab League peace plan.
Damascus, which blames "armed terrorist gangs" for the violence, meanwhile appealed to the international community to help it find an "honourable exit" to the crisis, notably by stopping the flow of weapons into Syria.
On the ground, four children were among 24 people killed when regime forces opened fire in several cities across the country after the weekly Muslim prayers, the Syrian Observatory for Human Rights reported.
The Observatory said 11 civilians were killed in and around Homs, while five died near Damascus, two in Daraa, cradle of anti-regime protests since March, four in the restive city of Hama and two in the northwestern province of Idlib.
Pro-democracy activists had called on citizens to turn out in support of a "dignity strike... which will lead to the sudden death of this tyrant regime."
An Arab League ministerial task force was due to meet Saturday in Qatar to mull a response to Syria after it refused to allow observers on its territory.
The pan-Arab bloc, which last month suspended Syria's membership and hit it with sweeping sanctions, has warned it of more punitive measures unless it complies.
The opposition Syrian National Council warned of a looming bloody final assault on Homs using the pretext of what the regime had called a "terrorist" attack Thursday on an oil pipeline.
"The regime (is) paving the way to commit a massacre in order to extinguish the revolution in Homs," said the SNC, a coalition of Assad opponents.
Homs, an important central junction city of 1.6 million residents mainly divided along confessional lines, is a tinderbox of sectarian tensions that the SNC said the regime was trying to exploit.
"The regime has tried hard to ignite the sectarian conflict using many dirty methods, which have included bombing and burning mosques, torturing and killing young men, and kidnapping women and children," the SNC said.
Witnesses in Homs, already besieged for months, have reported a buildup of troops and pro-regime "shabiha" militiamen in armoured vehicles who have set up more than 60 checkpoints, the SNC said.
"These are all signs of a security crackdown operation that may reach the level of a total invasion of the city," it added, calling for international organisations to take action.
US State Department spokeswoman Victoria Nuland said that Assad would be responsible for any further deaths and expressed Washington's deep concern for developments in Homs.
"There are reports today that the government may be preparing a very serious new assault on the city of Homs in a very large-scale way," said Nuland.
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London echoed Washington's concern, with Foreign Office minister Alistair Burt saying: "The Syrian government should immediately withdraw its forces from Homs and exercise restraint."
The regime's crackdown on dissent since mid-March has hit Homs particularly hard and activists say a great number of defecting soldiers have set up camp there to protect the protest movement.
"Our view is that President Assad bears responsibility for what the security forces of his country do, despite his comments to the contrary on television," Nuland said.
Assad, speaking to ABC News this week, denied responsibility for the bloodshed. He drew a distinction between himself and the military, saying only a "crazy" leader would kill his own people.
But Syrian foreign ministry spokesman Jihad Makdisi told a news conference in Damascus Friday evening that ABC had "distorted" Assad's comments.
"It deliberately deformed the president's words... by airing videos (of violence) to incite" action against Syria, said Makdisi.
He said Assad was "appalled by the ongoing violence" and has promised "accountability", adding that Damascus needed international help to stop the flow of weapons into the country as a way to end the unrest.
"We are appealing to the outside world and our brothers in the Arab world to help Syria (prevent the) channelling (of) weapons" into the country, Makdisi said, speaking in English.
"If we all work together we can find an honourable exit to the crisis."
UN chief Ban Ki-moon and UN human rights chief Navi Pillay both hit back at Assad's claim that the United Nations had inflated its figures for the number of people killed in the crackdown.
"All the credible information is that more than 4,000 people have been killed by the government forces," Ban said in Kenya.
Pillay told how more than 220 witnesses had been interviewed by UN human rights commissioners whose report was rubbished by Assad in the interview with ABC.
"It is first hand witness accounts, a great deal of information coming via Skype from inside the country," Pillay told a news conference at the UN headquarters.
Pillay is to brief the UN Security Council about Syria and the wider Middle East at a meeting on Monday, the council announced after what diplomats called "heated" talks on a French proposal to call in the rights chief.
Russia and China vetoed a resolution condemning the Syrian violence in October and there has been little discussion since.
Pillay said that the last time she discussed Syria at the council in August there were more than 2,000 dead.