Syrian security forces shot dead 13 civilians on Monday and Tuesday in the central protest hub city of Homs, rights activist Rami Abdel Rahman told AFP.
"Thirteen civilians were killed yesterday and today in several parts of Homs when the army opened fire as it carried out an operation in the city" to quash dissent, said the head of the London-based Syrian Observatory for Human Rights, reached by telephone from Nicosia.
Late Monday another activist had said that security forces swept into the flashpoint city and shot dead a civilian and wounded four others.
Several coaches packed with security force personnel entered the Khalidiyeh neighbourhood of Homs and afterwards gunfire was heard, said Abdel Karim Rihawi.
Signup to our newsletter and follow us on Facebook and Twitter!
The wounded were taken to the Al-Bir Hospital, said Rihawi, who heads the Syrian League for the Defence of Human Rights.
Fierce fighting rocked Homs at the weekend, with activists reporting that more than 30 people were killed in skirmishes between Christians, Sunni Muslims and Alawites from President Bashar al-Assad's minority community.
Activists have said the violence in Homs could spark a new and dangerous turning point in more than four months of pro-democracy protests, with Rihawi describing it as a "dangerous signal of the break-up of Syrian society."
Abdel Rahman said at the weekend the fighting in Homs erupted after three regime supporters kidnapped last week were killed and their dismembered bodies returned to their relatives.
"These clashes are a dangerous development that undermines the revolution and serves the interests of its enemies who want it to turn into a civil war," he said.
Activists say the Syrian government's crackdown on pro-democracy and anti-regime protests has left more than 1,400 civilians dead. Thousands more have been jailed.