Syrian government forces renewed their assault on the rebellious city of Homs on Tuesday, activists said, as the UN human rights chief raised fears of civil war.

Troops loyal to President Bashar Assad have been shelling Homs for more than a week to retake parts of the city captured by rebel forces. Hundreds are believed to have been killed in just over a week, and the humanitarian conditions in the city are worsening.

A damaged car is seen in Bab Amro in the Syrian city of Homs on Monday. (Reuters)

Homs was under "brutal shelling" on Tuesday, the Local Co-ordination Committees activist group said, citing its network of witnesses on the ground.

With diplomatic efforts bogged down, the conflict in Syria is taking on the dimensions of a civil war, with army defectors clashing almost daily with soldiers.

Meanwhile, Egypt circulated a UN General Assembly resolution Tuesday strongly condemning human rights violations by the Syrian regime and backing an Arab League plan aimed at ending the 11-month conflict in the country.

The draft resolution strongly supports the Arab League's decision to facilitate a Syrian-led political transition to a democratic political system, including by starting "a serious political dialogue between the Syrian government and the whole spectrum of the Syrian opposition."

Diplomats said the resolution could be put to a vote in the 193-member assembly as early as Thursday and is likely to be adopted by a wide margin.

More than 5,400 killed: UN

The draft resolution was finalized by Arab nations a day after UN human rights chief Navi Pillay decried Syria's escalating crackdown on civilian protesters and warned that the Security Council's recent failure to take action has emboldened President Bashar Assad's government to launch an all-out assault to crush dissent.

Pillay warned on Monday that the Security Council's failure to take action has emboldened the Syrian government to launch an all-out assault.

The uprising began last March as mostly peaceful protests against Assad's authoritarian rule, but has become more militarized in the face of the brutal military crackdown.

Pillay told the UN General Assembly that more than 5,400 people were killed last year alone, and the number of dead and injured continues to rise daily.

She said tens of thousands of people, including children, have been arrested, more than 18,000 reportedly are still arbitrarily detained and thousands more are reported missing. In addition, 25,000 people are estimated to have sought refuge in neighbouring countries and more than 70,000 are internally displaced.

"The breadth and patterns of attacks by military and security forces on civilians, and the widespread destruction of homes, hospitals, schools and other civilian infrastructure indicate approval or complicity by authorities at the highest level," Pillay said.

Envoy to Canada objects

In Ottawa on Monday, Syria's top diplomat in Canada struck back at the Harper government for what he said are "deplorable" sanctions that he insisted are harming innocent civilians in his country.

Bashar Akbik, Syria's top diplomat in Canada, blames terrorists and criminals for the violence in his country. (Mike Blanchfield/Canadian Press)

Bashar Akbik, Syria's charge d'affairs, levelled that accusation in an interview with The Canadian Press during which he steadfastly denied that the regime of President Bashar Assad is responsible for the killing of thousands of innocent civilians in a bloody 11-month crackdown on dissent.

Akbik blamed terrorists and criminals for the violence in his country. He said a Western-led "conspiracy" — with Saudi Arabia's collusion — is trying to overthrow his government and that conspiracy is responsible for the carnage that the United Nations says has left more than 5,400 dead.

"Hollywood"-style videos on the Internet that have fabricated scenes of government forces killing innocent civilians are part and parcel of the international plot, he said.

Also Monday, U.S. President Barack Obama's administration said it backs Arab League plans to end continuing violence in Syria but noted several obstacles to deploying a proposed international peacekeeping force to the country and withheld full endorsement of the idea.

The administration has said repeatedly it does not see a military solution to the crisis in Syria, yet U.S. officials indicated they would consider the Arab League call for peacekeepers and discuss it with various countries to see whether such an idea is feasible.

However, they stressed there would be difficulties in getting required UN Security Council authorization for a force.

Chief among the hurdles is opposition by Russia and China, which vetoed a far less ambitious Security Council action already this month. Russia has said peacekeepers could not be sent without Syrian government approval; officials in Damascus already have rejected the proposal, calling it unjustified interference in internal affairs.