United Nations observers entered Saturday the Syrian village in which a reported massacre this week blamed on forces loyal to President Bashar al-Assad left more than 200 people dead, activists said.
"The UN vehicles are now inside Tremseh village and the team is taking pictures of the area," Abu Ahmed al-Hamawi told dpa by phone from the central province of Hama, dpa reported.
If confirmed, the Tremseh massacre would be one of the biggest single incidents since the 16-month conflict started.
Their visit to Tremseh comes amid another day of violence in Syria, with a bomb explosion in a Christian area killing four, and some 19 people killed in the central province of Homs, according to activists.
Tremseh, which has a population of 7,000, is a mainly Muslim-Sunni village lying near the village of al-Qubeir, where at least 55 people had been already been killed earlier this month by al-Assad's forces and paramilitaries, according to the opposition.
Tremseh and al-Qubeir are in the vicinity of other villages mainly controlled by Alwaite - an offshoot of Shiite Islam - to whom al-Assad belongs.
Meanwhile, at least four people were killed Saturday in a bomb explosion in the Christian village of Mahradeh in Hama.
The victims comprised two women, a 13-year-old boy and a security man according to the opposition Syrian Observatory for Human Rights.
The blast targeted a military building, according to the London-based organization. The Syrian state news agency said the explosion had been caused by a truck loaded with explosives.
Activists based in Hama reported other explosions, which they said were followed by heavy machine gun firing. They gave no figures of possible casualties.
Elsewhere, hundreds of government troops backed by helicopter gunships and armoured vehicles attacked Khirbet Ghazaleh, a rebel stronghold in the southern Syrian province of Daraa, reported opposition activists.
Meanwhile, 19 people, including a pregnant woman, were killed by government forces in Homs, a key pro-opposition hub.
UN Secretary General Ban Ki-moon has called on the Security Council to urgently act to stop the bloodshed in Syria, saying its failure would give "a licence for further massacres."
Germany, Britain, France, the United States and Portugal have proposed a UN resolution that would give al-Assad's government 10 days to stop the use of heavy weapons on populated areas, or face tougher sanctions.
The draft resolution proposes extending mandate of the UN observer mission in Syria by 45 days.
Russia has again rejected any use of sanctions against its main ally in the region, and tabled a rival resolution that renews the UN observers' mandate, which ends on July 20, for 90 days.
The observers were dispatched to Syria in April to monitor a UN-brokered ceasefire that never held.
Meanwhile, Britain's Sky news reported, citing British intelligence officials, that Syrian forces have moved chemical weapons to Homs, where rebels have control of vast regions.
The report came a day after the Wall Street Journal quoted US officials as saying that Syria has begun moving parts of its vast arsenal of chemical weapons out of storage facilities.
The country's undeclared stockpiles of sarin nerve agent, mustard gas and cyanide have long worried US officials and their allies in the region.