A team of UN observers have inspected an area some six kilometres away from the Syrian village of Tremseh, where up to 200 people were reportedly killed by government forces this week, activists said Saturday.

A UN source confirmed to DPA that a team of observes managed to carry out a kind "of a reconnaissance trip" near Tremseh late Friday.

Pictures and videos posted online showed UN vehicles in an area near Tremseh, with citizens surrounding the car showing them blood-stained clothes and remains of shells.

"These are Russian weapons," shouted an angry man in the video.

There were no independent accounts on the number of dead or how they were killed in Tremesh, located in the restive province of Hama, but activists say between 150 and 250 were killed by government forces on Thursday.

Activists in the area reported a "relative calm" in and around Tremseh since late Friday.

The fresh bloodshed raised anger among western countries, which demand tougher actions against Syria. U.S. Secretary of State Hillary Rodham Clinton called Friday for an immediate ceasefire and for UN observers to be allowed to enter the site.

Amnesty International said the UN must be allowed "unfettered access to investigate such incidents."

"Without an independent presence to investigate the facts, it is impossible to verify what really happened," said Ann Harrison, Amnesty International's Middle East and North Africa Deputy Program Director