DAMASCUS - Both official media and an opposition group on Sunday branded as a failure a world powers deal on a transition plan for Syria a day after more than 80 people were reported killed in violence nationwide.

World powers meeting in Geneva on Saturday agreed a transition plan that could include current regime members, but the West did not see any role for President Bashar al-Assad in a new unity government.

Russia and China insisted that Syrians themselves must decide how the transition should be carried out rather than allow others to dictate their fate.

Moscow and Beijing, which have twice blocked UN Security Council resolutions on Syria, both signed up to the final agreement that did not make any explicit call for Assad to cede power.

Both official Syrian media and the opposition Local Coordination Committees (LCC) group demonstrated rare agreement on Sunday in slamming the outcome of the Geneva talks.

The meeting "failed," trumpeted Al-Baath, newspaper of the ruling party.

"The agreement of the task force on Syria in Geneva on Saturday resembles an enlarged meeting of the UN Security Council where the positions of participants remained the same," it said.

The LCC, which organises protests on the ground in Syria, said the outcome showed once again the failure to adopt a common position.

It called the transition accord "just one version, different in form only, of the demands of Russian leaders allied to the Assad regime and who cover it militarily and politically in the face of international pressure."

"The new agreement contains obscure turns of phrase that give the Assad regime's gangs another chance to play for time in suppressing the popular revolution and to silence it through violence and massacres."

At least 83 people were killed, mostly civilians, on Saturday, and hundreds more were trapped in Douma north of Damascus as regime forces stormed the town, the Syrian Observatory for Human rights said.

In the single most serious incident, mortar fire killed 30 civilians at a funeral in the town of Zamalka, 10 kilometres (six miles) east of Damascus, the Britain-based watchdog said.

The Geneva deal came despite initial pessimism about the prospects of the talks amid deep divisions between the West and China and Russia on how to end the violence that the Observatory says has killed more than 15,800 since March 2011.

UN and Arab League envoy Kofi Annan did not name names in Geneva, and said it was up to the Syrians to decide who they wanted in a unity government.

But he added: "I would doubt that Syrians... would select people with blood on their hands to lead them."

US Secretary of State Hillary Clinton made it clear that Washington did not see a role for Assad in the transition.

"Assad will still have to go. He will never pass the mutual consent test," she said.

French Foreign Minister Laurent Fabius took the same stance, saying: "It's clear that Assad must stand down," adding that the transition government "will exclude murderers."

British Foreign Secretary William Hague admitted the deal was a "compromise agreement" as Russia played up the fact that it had convinced other world powers that it would be "unacceptable" to exclude any party from the transition process.

A long-time Syria ally, Russia is loath to cast Assad aside, even as relations between Moscow and Damascus have cooled.

Russian Foreign Minister Sergei Lavrov said: "How exactly the work on a transition to a new stage is conducted will be decided by the Syrians themselves."

"There are no demands to exclude from this process any one group. This aspect had been present in many of our partners' proposals. We have convinced them that this is unacceptable."

Chinese Foreign Minister Yang Jiechi also stressed that "outsiders cannot make decisions for the Syrian people."

Annan warned at the opening of the meeting that history would not look favourably on leaders who failed to chart a strategy to end the bloodshed.

A failure to unite also raised the spectre that the deadly conflict in the strategic Middle East country could spill over to the region and expose the world to fresh threats, the former UN chief said.

"History is a sombre judge -- and it will judge us all harshly if we prove incapable of taking the right path today," Annan told the five permanent Security Council members -- the United States, Russia, Britain, China and France -- as well as regional powers Qatar, Turkey, Kuwait and Iraq.

While the violence rages in Syria there is also mounting concern about the destabilising impact it has on the region, in particular Jordan and Lebanon.

And the Turkish-Syrian border remains a potential flashpoint.

Turkey has sent tanks, troops and missile batteries toward the frontier, after Syria shot down a Turkish jet just over a week ago.