(CNN) — Syrian forces shelled Houla early Thursday, opposition activists said, days after shadowy men went door-to-door in the town, slaughtering families with knives and guns.
The attacks started shortly after United Nations observers left the town, said a local resident whom CNN is not naming for safety reasons.
Government troops fired dozens of mortars and rockets, killing two people, opposition activists said.
An additional young boy was killed by sniper fire, according to the London-based Syrian Observatory for Human Rights.
CNN cannot confirm death tolls or reports of violence from Syria because the government limits access to the country by foreign journalists.
The reported attacks highlight a conflict that has spiraled out of control as the call for President Bashar al-Assad’s ouster that began in March 2011 has devolved into a brutal crackdown against the protesters by the government.
In the massacre in Houla on Friday, most of the more than 100 victims killed were children and women, sparking international outrage that led Western nations to expel Syrian diplomats in a coordinated move against the regime.
The United States, the Netherlands, Australia, Britain, France, Germany, Italy, Japan, Spain, Bulgaria, Turkey and Canada announced that they are expelling Syrian diplomats.
Susan Rice, the U.S. ambassador to the United Nations, said the massacre was carried out by Shabiha militias or local gangs acting on behalf of the regime.
Syria has repeatedly denied involvement. Bashar Jaafari, the nation’s U.N. ambassador, said the government will finish its investigation into the massacre this week.
“And all of us will know for sure the identity of the perpetrators,” he said.
Since the conflict began, the government has blamed the violence against civilians on armed terrorist groups.
Alex Thompson, chief correspondent for Channel 4 News, visited Houla and expressed skepticism about the government’s claim.
“The question you have to ask is, ‘How was it 100 armed militia were able to come in and slaughter family after family, in an area which was an intensive shelling zone prior to them arriving, and yet when they came in the area, no shells fell on them?'” he told CNN’s “Anderson Cooper 360” on Wednesday night.
Syrian opposition fighters issued the government a Friday afternoon deadline to cease fire, pull out troops from residential areas and allow humanitarian aid.
The Free Syrian Army, which mainly comprises of military defectors, did not say what will happen if the government fails to comply.
“Our national, moral and humanitarian duty make it necessary for us to defend and protect our civilians and their cities, towns, blood and dignity,” the group said in a statement.
The ultimatum lists a series of demands in a peace plan implemented last month and brokered by United Nations special envoy Kofi Annan.
“Immediately halting gunfire and all violence, pulling out all the troops, tanks and machinery from residential areas, allowing humanitarian aid to reach all stricken areas, releasing all prisoners and allowing media access,” said Col. Qasim Saad Eddine, the group’s spokesman.
Eddine also called for freedom to demonstrate, an end to attacks on U.N. monitors in the nation and a dialogue on power handover.
Despite the Annan peace plan, violence has continued almost daily.
Clashes continue unabated, with regime forces and police shelling a Homs neighborhood Thursday, said the Local Coordination Committees of Syria.
A day earlier, at least 74 people were killed nationwide and 13 bound and shot bodies were discovered in eastern Syria, the head of the U.N. observer mission said.
The United Nations estimates 9,000 people have died since the protests began last year, while activist groups put the death toll at more than 11,000.
Meanwhile, Syrian authorities freed 500 prisoners arrested for their alleged involvement in the 15-month uprising against the government, state TV reported Thursday. No more information was immediately available.