London  - Investigations into the recent murders of two soldiers and a police officer in Northern Ireland were thrown into disarray Wednesday when six men were freed from police custody after winning a legal challenge against their detention.

However Colin Duffy, one of the suspects and a former member of the now inactive Irish Republican Army (IRA) paramilitary group, was immediately re-arrested, his lawyers said.

The suspects were released from custody at Antrim police station, north of Belfast, within an hour of a High Court ruling that described their prolonged detention as "unlawful."

With coats draped over their heads, they were driven away at high speed from the police station where they had been held since March 14.

Four of the detainees, including Duffy, were held in connection with the murder of two British soldiers on March 7, and two were suspected of the killing of the police officer two days later.

The deadly attacks marked a chilling return of terrorist violence to the province which had enjoyed a period of stability since the signing of the 1998 peace agreement.

The court ruling and the subsequent release of the suspects mark a setback for the Police Service of Northern Ireland (PSNI), but also for the British government whose controversial anti-terror legislation, allowing the detention of suspects for 28 days without charge, has been widely criticized.

Northern Ireland's Lord Chief Justice, Brian Kerr, ruled that an extension of their detention, granted by a county court judge over the last weekend, was "unlawful."

Two IRA splinter groups, the Real IRA and the Continuity IRA, which oppose the peace agreement and the disbanding of the IRA, have claimed responsibility for the recent killings.

Two British soldiers in their early 20s were gunned down outside Massereene barracks, near Belfast, on March 7, and Stephen Carroll, a 48-year-old police officer, was killed with a shot to his head while answering a call for help in the southern town of Craigavon two days later.

Two men, a 17-year-old local youth and a 37-year-old former Sinn Fein councillor, have been charged in connection with the Carroll murder. Both have denied the charges.

Wednesday's court ruling was welcomed by Gerry Adams, the president of Sinn Fein, a party with previously close links with the IRA which has, however, renounced violence and is now in a power-sharing regional government with Protestants in Northern Ireland.

"Detaining people for periods extending beyond human rights best practice is simply not acceptable and must not happen in the future," Adams said Wednesday.

Paul Goggings, the state secretary responsible for policing and justice in Northern Ireland, said the High Court ruling related to a "technical matter" and the attacks remained subject to a "strong and ongoing police investigation." (dpa)