N.Ireland's police chief says militants number 300

Militants who want to end British control of Northern Ireland by force number around 300, the province's police chief said on Sunday, as his officers questioned more people over sectarian killings.

The Real IRA, a splinter group of the Irish Republican Army (IRA) which formally ended its military campaign against British rule in 2005, shot dead two soldiers on March 7 in the deadliest act of violence in Northern Ireland in over a decade.

The attack was followed two days later by the killing of a police officer by another splinter organisation, the Continuity IRA.

"These groups are small. The Real and Continuity IRA are disrupted, infiltrated and disorganised," Chief Constable Hugh Orde wrote in the News of the World on Sunday.

"We are working flat out with the security services and other specialists to disrupt and arrest them and lock them up for the rest of their lives."

Police were questioning four people over the shooting of the soldiers, including one man arrested on Saturday night.

The arrest of a well-known pro-Irish nationalist in the town of Lurgan, southwest of Belfast, prompted groups of youths to pelt police with bricks, stones and petrol bombs on Saturday. One officer was hurt when he was struck on the arm by a brick.

Police also arrested a man and a woman on Saturday in connection with the shooting of the police man and seized a gun and ammunition. A total of five people are now being questioned about his death.

The attacks shattered a relative calm brought by a 1998 peace deal which ended 30 years of violence between the IRA, seeking a united Ireland, and groups wanting to maintain the union with Britain.

Politicians on both sides of Northern Ireland's sectarian divide have said the violence will not derail the peace process, but many people in the province fear more attacks will happen.

Orde said the militants had tried at least 25 times to kill police officers over the last 18 months. In late January, a large car bomb was discovered and defused around 30 miles south of Belfast.

The Real IRA and the Continuity IRA do not have widespread grassroots support but pro-Irish nationalists fear support could grow for them if the police, still viewed with mistrust in many nationalist neighbourhoods, use aggressive tactics in flushing them out.

The deployment of British military specialists to help catch the militants is also controversial in Northern Ireland, where special forces such as the SAS operated during decades of violence between the majority Protestant population, who want the province to remain part of Britain, and minority Catholics.