ANTALYA, Turkey (Reuters) - Syrian forces killed at least 13 civilians in the town of Rastan on Thursday in one of the most ferocious military assaults to crush dissent against President Bashar al-Assad's rule, human rights campaigners said,
The killings raise the death toll from attacks by tanks backed by troops that encircled several towns and villages in the central province of Homs this week to at least 56 civilians, they added.
"These are killings we documented, but the real numbers are definitely more. To those who want retribution I say: this is the age of international justice and the killers will be held accountable," Ammar Qurabi, head of the Syrian Human Rights Organization, said at a meeting of Syria's opposition in Turkey.
In a pattern seen in other urban centers that have seen street demonstrations, civilians in Rastan were killed by gunfire from snipers and security forces as they stormed neighborhoods in the town of 60,000 people north of the city of Homs and imposed a curfew, the activists said.
At least 200 people have been arrested in Rastan since the military assault began on Sunday, said Qurabi.
"There have been rare instances of people who have seen their parents, wives or children being killed, (people) taking their personal weapons and trying to resist. But they were smothered by the overwhelming and unjustifiable force being used by the authorities," he added.
Qurabi said his Organization had the names of 1,113 civilians killed since the uprising against the 11-year rule of Assad erupted on Syria's southern Hauran Plain on March 18.
A military crackdown to quell demonstrations has intensified in the last several weeks.
The official state news agency said four soldiers were killed by "armed terrorist groups" in Rastan on Wednesday and were buried on Thursday.
Activists said there has been numerous cases of secret police shooting soldiers for refusing to fire at protesters or to participate in attacking population centers.
Syrian has barred most international media, making it difficult to verify accounts of the violence.
(Reporting by Khaled Yacoub Oweis; Editing by Jon Boyle)