A prominent human rights group says it fears Syria is torturing dozens of men detained last Saturday and Sunday after mass arrests outside of the capital, Damascus.

Amnesty International says Syria is holding the men incommunicado after arbitrarily arresting them in raids in the suburb Qatana, southwest of the capital. The group has demanded that Syria reveal the detained men's whereabouts and ensure they are protected from torture and other ill treatment.

Earlier, Syrian rights activists and witnesses said pro-government forces had shot and killed at least 13 people since Monday in the central city of Homs, a center of recent protests against President Bashar al-Assad.

The activists and residents of Homs say Syrian troops and pro-Assad militiamen opened fire on a funeral procession outside the city's Khaled bin Al-Waleed mosque Tuesday, killing at least three people. The mourners had gathered for the funerals of 10 people killed by security forces on Monday.

Some residents said people were hiding in their homes as pro-government forces fired indiscriminately in the streets.

This violent government crackdown follows two days of sectarian battles in Homs between members of Mr. Assad's Alawite minority and Syria's majority Sunnis.

The fighting erupted Saturday when the dismembered bodies of three Alawite supporters of Mr. Assad were returned to relatives in the city. Activists said Assad loyalists reacted by going on a rampage, setting fire to and breaking into Sunni-owned shops. About 30 people were killed in the battles on Saturday and Sunday.

Rights activists accuse the Syrian government of trying to provoke sectarian conflict in Homs to weaken a four-month opposition uprising against Mr. Assad's 11-year autocratic rule.

It is difficult to verify the accounts of the violence in Homs because the Syrian government has barred foreign media from reporting and traveling freely in the country.