United Nations monitors in Syria have reached the site of an alleged massacre in Hama province, as Syrian troops were reported to be shelling a neighbourhood in the central city of Homs in apparent preparation to storm an area that has been in rebel hands for months.
UN sources and activist reported on Friday that members of the UN monitoring mission had entered the village of Mazraat al-Qubeyr two days after at least 78 people, including women and children, are alleged to have been killed there.
"The observers first headed to the village of Maarzaf where the victims were buried and then to al-Qubeyr to survey the damage from army shelling," activist Abdel Karim al-Hamwi said.
He said soldiers at a checkpoint in Maarzaf ordered residents not to speak to the observers or face reprisals.
While the opposition blamed pro-Assad fighters for the killings, the SANA state-run news agency said that "an armed terrorist group" had committed an "appalling crime" in Mazraat al-Qubayr, a small farming town in Hama province of about 160 people, mostly Bedouins.
Activists on Friday reported anti-government protests across the country under the banner "Revolutionaries and traders, hand-in-hand until victory," in an attempt to encourage traders to strike in support of the uprising.
Activists said that government troops used heavy weaponry in Homs' Khalidiyah neighbourhood, firing shells at a rate of 10 per minute, making it the most intense shelling since the beginning of the uprising in March 2011.
In other parts of the country, the Local Co-ordination Committees, an opposition activist network, reported clashes between government forces and opposition fighters in Damascus neighbourhood of Kafar Souseh.
The group also said that an explosion rocked the neighbourhood of Qadam in the capital but had no immediate word on casualties.
Meanwhile, a video has emerged of Syrian soldiers apparently abusing the bodies of dead opposition activists in Idlib near the Turkish border.
The gruesome footage, recorded in March but only posted online on Friday, shows what appears to be Syrian soldiers kicking and stepping on bodies. The victims were said to be volunteers who moved wounded people across the border into Turkey.
The pictures were taken by one of the soldiers and leaked to the opposition, activists said.
Friday's arrival of the UN monitors in Mazraat al-Qubeyr in Hama comes after they had been blocked from nearby villagers by Syrian forces and residents a day earlier, and amid concern for their safety on the ground.
UN patrols in Syria have in several instances been deliberately targeted with heavy weapons, armour-piercing ammunition and a surveillance drone, UN Secretary-General Ban Ki-moon told the Security Council, according to a senior UN official.
The official, speaking on condition of anonymity because Thursday's council meeting was private, said Ban also reported repeated incidents of firing close to UN patrols, apparently to get them to withdraw.
Susan Rice, the US ambassador to the UN, likened the monitors to "300 sitting ducks in a shooting gallery, one IED from a disaster," at the Security Council meeting.
An improvised explosive device, or roadside bomb, exploded in front of a convoy of UN ceasefire monitors last month, without wounding anyone.
The Security Council has ordered a review of the mission to be ready before its 90-day mandate ends on July 20.
According to diplomats and UN officials, options being studied range from sending more observers with armed protection to a complete withdrawal if the UN monitoring mission suffers casualties. All stressed that no decision had yet been taken.
Ban and UN-Arab League envoy Kofi Annan say government-inspired violence has been reduced in areas where monitors are present. But neither wants to increase the force because of the threat to lives, diplomats said.
In-depth coverage of escalating violence across Syria
So far no UN monitors, nearly all senior military officers hailing from nearly 50 countries, have been hurt. But a UN official said: "Some of the countries are not very happy about the risks their people are going through."
The US has said it cannot guarantee that the monitoring mission will be renewed because of Assad's refusal to carry out an international peace plan.
Ban and Annan have in turn highlighted the criticism that the force has faced from many Syrians, who cannot understand why the monitors are in Syria to observe the violence and not to halt it.
Britain's UN ambassador Mark Lyall Grant said he and other UN envoys have asked for a review of the mission.
"There is a great deal of vulnerability on the observer mission at the moment," Lyall Grant told reporters after hearing Ban's list of attacks.
"In those circumstances, it's clear that the current configuration of the mission is not sustainable in the long term, and so I think it's our duty, it's our moral duty, to consider what other options there will be going forward."