The opposition collective Syrian National Council said troops stormed a neighborhood and corralled about 350 young men into a square by a mosque and publicly gunned down the men, CNN reported.
Homs is a stronghold for anti-government rebels, who have been fighting the regime of President Bashar Assad since March of last year.
Elsewhere in Syria's largest city and commercial hub of Aleppo, government forces rained artillery on rebel positions, The Sunday Telegraph reported.
Abdulaziz al-Salameh, head of the Aleppo revolutionary council, told the British newspaper the rebels weren't going to back down.
"We are prepared to see the city destroyed before we give it up," he said.
Syrian state-run TV said government forces had killed 12 rebels and destroyed five of their vehicles.