Russia insisted on Monday that it was not a supporter of Bashar al-Assad's Syrian government but also told world powers to concentrate on ending spiralling violence rather than regime change.

The comments from Foreign Minister Sergei Lavrov during talks with British counterpart William Hague came as Russia faced mounting pressure to join global calls for the Syrian strongman's ouster after the horrific massacre in Houla.

Lavrov said "both sides" were to blame for the killing spree while adding that -- like any government hit by internal conflict -- the Assad regime should bear the brunt of the responsibility.

Russia has been condemned for vetoing two rounds of sanctions against Assad's regime and continues to supply arms to its Soviet-era ally despite fears its weapons may be used to shell Syrian villages and towns.

"For us, who is in power in Syria is far from the most important thing," Lavrov said at a joint news conference with Hague. "What is important is ending the violence."

"We do not support the Syrian government. We support the plan of (UN-Arab League peace envoy) Kofi Annan."

Western powers have been watching closely whether last week's massacre in which at least 108 people -- almost half of them children -- were killed would finally force a marked change in Russia's stance.

Moscow is believed to hold the most sway with Assad's regime among the global powers and its support is seen as imperative for any lasting solution to work.

Lavrov did not squarely blame the Assad regime for the Houla massacre and said both the regime's forces and the armed opposition were involved.

"Here we have a situation where both sides clearly had a hand in the fact that peaceful citizens were killed," Russia's top diplomat said.

"The government bears the most responsibility what happened, and we discussed this. This is the case with any government."

Russia and China have both questioned why some of those killed appeared to have died in close combat rather than the shelling blamed an Assad's troops.

Hague for his part put the feared death toll from more than 14 months of bloodshed at 15,000 and said Russia needed to put more pressure on Assad to avoid even more terrifying and uncontrollable loss.

"It is not as if the alternatives in Syria are the Annan plan or the Assad regime retaking control of the country," Hague said.

"The alternatives are the Annan plan or ever increasing chaos in Syria and the descent closer and closer to all-out civil war and collapse."

Their meeting came after The New York Times reported the administration of US President Barack Obama was considering working with Russia on a plan for Assad's departure under a proposal modelled on the transition in Yemen.

The paper reported that Obama intended to bring up the idea during his first meeting with Vladimir Putin since the Russian president's election to a third term in March.

The report added that the option had gained so much currency in Moscow it had become known as the "Yemensky (Yemeni) variant" in US diplomatic circles.

Lavrov did not comment on the report directly but pointed out that the Annan plan Moscow backed called for direct negotiations "between the Syrian government and the opposition" rather than Assad himself.

"We are deeply worried that the Annan plan is being implemented unsatisfactorily. We are still far from our goals," Lavrov said.