"Most of the bodies had traces of torture, some were burnt alive and others were slaughtered with knives," Omar Homsi, an activist based in the restive province of Homs, told dpa.
"The bodies belong to 28 women, 23 children and six men," Homsi said.
He added that sixteen of the dead women had allegedly been raped before they were killed. The incident prompted the Syrian National Council (SNC) -- a group of prominent dissidents -- to call for an immediate emergency meeting at the UN.
"The Syrian National Council is making the necessary contacts with all organizations and countries that are friends with the Syrian people for the UN Security Council to hold an emergency meeting," the council said in a statement.
"The world community cannot stay silent anymore," SNC member Walid al-Buni told dpa from Istanbul.
The head of the London-based Syrian Observatory for Human Rights, Rami Abdul Rahman, called for the formation of a UN investigative committee to look into the latest violence in Homs.
On Sunday, Karam al-Zeitoun was the scene of heavy shelling targeting rebels of the opposition Free Syrian Army, who were hiding in the area.
State television blamed "armed terrorist gangs" on Monday for the killings in Homs.
"The terrorists had kidnapped residents of Homs, killed them and then made video footage of the bodies in an attempt to discredit Syrian forces," state television reported.
"We have been used to the escalation by armed terrorist groups before meetings at the Security Council, with the aim of inciting stances against Syria," state news agency SANA quoted an unnamed official as saying.
The violence has caused many to flee the province.
"Hundreds of families fled Homs overnight, notably from the Karam al-Zeitoun neighbourhood, for fear of new massacres by regime forces," Abdul Rahman said in a statement.
Pictures posted online by activists showed the bodies of five children who were disfigured after apparently being hit with sharp objects.
Funerals were held in the nearby Deir Balba neighbourhood for some of those who had been killed. Crowds followed the funeral march of some 26 bodies, chanting, "Where is the international community?"
Homsi told dpa that the funerals were held to the sounds of exploding shells and machine gun fire, echoing from nearby areas.
Protests at the killings erupted in several cities Monday, including the capital Damascus.
Elsewhere, Syria's military continued pounding rebel strongholds in the northern Idlib province as well as Daraa in the south.
An army vehicle was ambushed by rebels in Daraa, killing three soldiers, activists said.
News coming out of Syria cannot be independently verified as the government has banned journalists from entering restive areas. The UN has put the death toll at more than 7500, including 500 children, in the year since a crackdown began on protesters seeking the ouster of President Bashar al-Assad.
The alleged massacre came a day after UN-Arab League envoy Kofi Annan visited Damascus.
"It's going to be difficult but we have to have hope," Annan said after two meetings with al-Assad.
Observers have said Annan appeared to have failed to overcome the refusal of both al-Assad and the opposition to start talks.
Reports of the alleged atrocities in Homs are likely to top the agenda of the UN Security Council foreign ministers meeting in New York this week, the Doha-based Al Jazeera television said.
According to Arab media, US Secretary of State Hillary Rodham Clinton and Russian Foreign Minister Sergei Lavrov are to hold bilateral talks ahead of the meeting.
