Gangs of Roman Catholics set street bonfires and threw rocks, bottles and firebombs at security patrols early Tuesday after two Catholics were killed, apparently by Protestant extremists. The sporadic rioting in Catholic areas that began Monday night also marked the 17th anniversary of Britain's abandoned policy of detaining suspected guerrillas without trial. Police believe the two Catholics slain Monday were killed in reprisal for attacks last week by guerrillas of the predominantly Catholic Irish Republican Army in Northern Ireland, England and West Germany that killed six people and wounded 37. A spokesman at Belfast's police headquarters said no violence was reported during the day Tuesday. Police said security forces came under 83 separate attacks during the overnight fighting, but the spokesman said fewer than 500 people probably were involved in the clashes that occurred throughout the British province. Officials reported eight policemen were hurt, none seriously, and four of 12 civilians injured were hospitalized. The IRA and its supporters continue to commemorate the introduction of the internment law on Aug. 9, 1971, even though it was abandoned amid worldwide criticism in 1975. Officials said police and soldiers were attacked with bombs, rocks, bottles and bricks and the patrols responded by firing plastic bullets. Some shots were fired at police, the officials said, but they did not report any gunshot casualties and said at one point security forces fired live ammunition into the air to disperse rioters. Eleven people, including two teen-age girls, were freed on bail by courts after being charged with riotous behavior. An 18-year-old man from Catholic west Belfast was charged with throwing a gasoline bomb and assaulting police and remained in jail. Some bonfires flamed out of control and damaged buildings, including a Baptist church, before the night's violence subsided with demonstrators making their traditional protest of banging garbage can lids. The two men killed Monday were Seamus Morris, 17, shot to death on a Belfast street, and Peter Dolan, 25, a beer-truck deliveryman slain when he tried to block the gunmen's getaway. Their deaths raised the known death toll to 2,675 from the sectarian violence that began in 1969. Stanley Whittington, president of the Methodist church in Ireland, called for the determined pursuit of ``mindless murderers'' who cross the border to take refuge in the Irish Republic. He spoke at the funeral of William Hassard, 60, one of two construction men shot to death last Thursday by IRA terrorists because they were working at a police station at the border town of Belleek. The IRA seeks to unite Northern Ireland, where Protestants outnumber Catholics 3-2, with the predominantly Catholic Irish Republic.