Dozens of civilians were killed in cold blood in Homs, the Syrian government and opposition said on Monday, although they disputed responsibility for what both sides called a massacre.

The carnage in Homs, as well as an army assault on Idlib city in the northwest, coincided with a weekend visit to Syria by U.N.-Arab League envoy Kofi Annan, who was seeking agreement on a ceasefire, humanitarian access and a political dialogue.

This is the beginning of a process and the joint special envoy feels the process is on the right track, Annan's spokesman Ahmad Fawzi said from Qatar on Monday.

He said the former United Nations chief, who held two rounds of talks with President Bashar al-Assad, was concerned that violence was raging on, despite the start of his mediation.

The government and opposition each said the other side was to blame for the killings in Homs, where Syrian forces retook a rebel-held district on March 1 after a 26-day siege.

The terrorist armed groups have kidnapped scores of civilians in Homs, killed and mutilated their corpses and filmed them to be shown by media outlets, state news agency SANA said.

Footage posted by opposition activists on YouTube showed men, women and children lying dead in a blood-drenched room.

The Local Coordination Committees of Syria, a grassroots opposition network, said at least 45 women and children had been stabbed and burned in the Homs district of Karm al-Zeitoun.

It said another seven people were slain in the city's Jobar district, which adjoins the former rebel bastion of Baba Amr.

Activists contacted in Homs accused pro-Assad Alawite shabbiha militiamen of carrying out the killings.

Waleed Fares, an activist in Homs's Khalidiyah district, which is about one km from Karm al-Zeitoun, said that 30 to 40 tanks had arrived in Karm al-Zeitoun on Sunday night.

We know now that four families have been killed by shabbiha. We have 21 names and we are trying to confirm the names of the rest, he told Reuters via Skype, adding that the victims were all from Syria's Sunni Muslim majority.

It's quiet now but I have been hearing gunfire all night.

Fares said most of the killings occurred in Karm al-Zeitoun, but some took place in other districts. The Free Syrian Army helped move the bodies to one place. Otherwise the regime forces would have hidden the evidence, he said.

Syrian government restrictions on the media have made it hard to assess conflicting reports by the authorities and their opponents since an uprising against Assad began a year ago.

In the rebellious southern city of Deraa, a car bomb planted outside a girls' school killed one schoolgirl and wounded 25 others, opposition activist Maher Abdelhaq said, adding that pupils there had taken part in anti-Assad protests.

U.N. MEETS ON ARAB REVOLTS

The Security Council holds a special meeting on Arab revolts later on Monday and U.S. Secretary of State Hillary Clinton will meet Russian Foreign Minister Sergei Lavrov on the sidelines.

Russia and China have blocked attempts to pass a Security Council resolution condemning Damascus for its attempts to crush the rebellion, in which the United Nations says well over 7,500 people have been killed. Syrian authorities said in December insurgents had killed more than 2,000 soldiers and police.

The United States has drafted a new resolution, but Washington and Paris say they doubt it will be accepted.

China sounded an optimistic note, but gave no details.

China has actively participated in discussion about this draft resolution, and raised its ideas about revising it, Foreign Ministry spokesman Liu Weimin said on Monday.

We also support the international community playing an active role in a political solution to the Syria issue.

China and Russia, as well as Western and Arab nations, have voiced support for Annan's peace mission, but no common ground has emerged between Assad, who is bent on crushing dissent, and his opponents, who are determined to overthrow him.

The situation is so bad and so dangerous that all of us cannot afford to fail, Annan said in Damascus on Sunday.

Fawzi, his spokesman, said Annan had met the emir and prime minister of Qatar in Doha on Monday and was heading for Ankara for talks with Turkey's prime minister and foreign minister.

Annan has said he wants a ceasefire and access for humanitarian aid agencies to civilians in strife-hit areas as a first step before a political dialogue among all parties.

Moscow and Beijing want any international blame for the violence to be apportioned evenly and say both sides should be encouraged to stop fighting. Saudi Arabia and Qatar have taken a hawkish line, calling for the rebels to be armed.

Annan plans to pursue contacts with opposition factions, including the Syrian National Council, the National Coordination Body, the Free Syrian Army and others, Fawzi said.

We have to get the opposition parties to unify under one umbrella and then we have to convince the government to come and meet them in whichever venue he (Annan) proposes, he added.

(Additional reporting by Ben Blanchard in Beijing and Yasmine Saleh in Cairo; Writing by Alistair Lyon; editing by Peter Millership)