UN-Arab League international envoy Kofi Annan has condemned the massacre of 220 people in the village of Tremseh by pro-regime Shabiha militia after heavy shelling.

The international media have attempted to contact sources in the area with no success. Security forces reportedly cut internet and phone connections before they shelled and stormed the town.

Unverified footage posted on social media showed graphic images of dead and wounded Syrian rebels killed in Tremseh, which is 35km (20 miles) north of Hama.

An opposition activist from the village told Reuters that Alawite militiamen supporting President Bashar al-Assad attacked Tremseh after rebels pulled out from the village because of heavy shelling. The militia executed villagers with guns and knives and burnt down homes, said the activist.

Annan said he was "shocked and appalled" to hear confirmation of the use of heavy weaponry such as tanks and helicopters.

"This is in violation of the government's undertaking to cease the use of heavy weapons in population centres and its commitment to the six-point plan," he said.

"I condemn these atrocities in the strongest possible terms. It is yet another reminder of the nightmare and the horrors Syrian civilians are being subjected to."

He did not mention, though, the carnage committed on the ground by Assad's loyal Shabiha militia.

Annan held talks with Russia's foreign minister Sergei Lavrov to discuss the Syrian crisis.

A staunch defender of Assad, Russia urged Annan to work more closely with the Syrian opposition to end the violence.

Russia shifts position

"We do not see our partners being as ready [as Russia] to work with the opposition and Kofi Annan is the main mediator of this process," deputy foreign minister Gennady Gatilov told Interfax.

His stand may represent a slow shift in Russia's position on the conflict.

Putin has been seeking reassurances that Russia would hold its pivotal position in the Middle East country even if Assad goes.

Moscow said it would not agree to a threat of sanctions to end the conflict. The UN Security Council wants to extend its monitoring mission in Syria.

Russia also opposes a Syria peacekeeping operation put forward by UN Chief Ban Ki-moon.

Meanwhile, the opposition Syrian National Council (SNC) has called on the UN Security Council to pass a binding resolution against Assad after the Tremseh killing.

"To stop this bloody madness which threatens the entity of Syria, as well as peace and the security in the region and in the world, requires an urgent and sharp resolution of the Security Council under Chapter VII [of the UN Charter] which protects the Syrian people," said the SNC.