Syrian troops going house to house have detained more than 3,000 people in the past three days in the rebellious town of Rastan, which saw some of the worst fighting of the 6-month-old uprising recently, activists said Monday.

Over the past week, the military fought hundreds of army defectors who sided with anti-regime protesters in Rastan. The fighting demonstrated the increasingly militarized nature of the uprising and heightened fears that Syria may be sliding toward civil war.

The activist group Local Coordination Committees said fighting in the town has now stopped after the military operation that left dozens dead. The group and a Rastan activist confirmed about 3,000 in the town of 70,000 had been detained. The activist told The Associated Press by telephone that the detainees are being held at a cement factory, as well as some schools and the Sports Club, an enormous, four-story compound.

"Ten of my relatives have been detained," said the activist, who asked that he be identified only by his first name Hassan for fear of retaliation. Syria's opposition movement has until now focused on peaceful demonstrations, although recently there have been reports of protesters taking up arms to defend themselves against military attacks. Army defectors have also been fighting government troops, particularly in Rastan, the town just north of Homs that government forces retook on Saturday.

The fears of civil war, possibly along sectarian lines, were also heightened by the assassination Sunday of the 21-year-old son of Syria's top Sunni Muslim cleric - the latest in a string of targeted killings.

The state-appointed cleric, Grand Mufti Ahmad Badreddine Hassoun, is considered a loyal supporter of President Bashar Assad's regime, heading a host of regime-backed Sunni clergymen who have been a base of support for the president's ruling Alawite sect.

Syria's volatile sectarian divide means that an armed conflict could rapidly escalate in scale and brutality. The Assad regime is dominated by the Alawite minority, an offshoot of Shiite Islam, but the country is overwhelmingly Sunni Muslim. Alawite dominance has bred resentments, which Assad has worked to tamp down by pushing a strictly secular identity for the state.

He has exploited fears of a civil war by portraying himself as the only power who can keep the peace.

The uprising began in mid-March amid a wave of antigovernment protests in the Arab world that have so far toppled autocrats in Tunisia, Egypt and Libya. Assad has reacted with deadly force that the United Nation's estimates has left some 2,700 people dead.