The BBC reported people fleeing the restive city say security forces had been conducting summary executions and cutting throats of prisoners.
The British broadcaster reported one woman, who had walked three days to escape, said her 12-year-old son's throat was cut Friday, a day after rebel fighters left the Baba Amr district in Homs.
The woman said her son was among 36 men and boys from the area who had been detained and killed.
Meanwhile, Syrian rebels said they were going on the offensive near Damascus after government troops launched rocket attacks on the western city of Rastan.
Reports out of Syria, which are difficult to confirm because of the lack of access by international journalists, suggest President Bashar Assad's troops are killing civilians in an attempt to wipe out dissidents, CNN reported Monday.
The Syrian Network For Human Rights said 66 people, including women and children, were killed Sunday by government troops. Most of the deaths occurred in Homs and Rastan.
The Syrian government alleges an 11-year-old boy was killed and five people were injured after a bomb planted by the opposition exploded in Aleppo.
The Free Syrian Army, largely composed of regime defectors, has mostly retreated from Rastan, CNN reported. The rebel army, however, said it was able to launch an attack on an air force intelligence building in Harasta, near Damascus, Sunday night.
The International Committee of the Red Cross said aid workers have still not been allowed in the Baba Amr neighborhood of Homs, where there is little or no running water or electricity, temperatures have dropped precipitously and snow had begun falling.
The BBC said Syrian state television has been showing footage of workers clearing away rubble from the weeks of attacks on the neighborhood, which the government says has been cleared of "armed terrorist groups."
U.N. humanitarian chief Valerie Amos said Monday that Syria had approved her visit and she planned to travel there Wednesday. She said she would urge all parties to allow access to humanitarian aid.
Israel has offered humanitarian assistance to Syrian residents.
"The state of the Jewish nation cannot sit still while horrors are taking place and people are losing their world in a neighboring country," Foreign Minister Avigdor Lieberman said. "It is our moral duty to provide aid and awake the world to stop the manslaughter."
The United Nations estimates more than 7,500 people have died and 70,000 have been displaced since the beginning of the Syrian conflict last year.