BELFAST, Northern Ireland (AP) _ At least three men killed a truck driver on Thursday in a machine-gun attack claimed by the Irish Republican Army, and a Protestant paramilitary group said it killed an IRA backer the day before.

Two witnesses to Wednesday's attack leveled charges of collusion between security forces and Protestant paramilitary groups in this British province.

The IRA unit in East Tyrone said its members shot the unidentified driver, who delivered construction materials to police stations and military bases. It said his employer ignored warnings to stop working for security forces.

The IRA has targeted construction firms in an effort to prevent repairs on bomb damage it inflicts on security bases. The victim's employer, Henry's of Magherafelt, earlier lost a director in a shooting and a manager in a bombing.

Police said the man was driving a concrete mixer when he was attacked outside Donaghmore village near Dungannon, 40 miles west of Belfast. The machine-gunners fired at least 30 shots before fleeing in a car, police said.

The outlawed Protestant Ulster Volunteer Force on Thursday night claimed responsibilty for killing Sam Marshall, 31, on Wednesday shortly after he left the Royal Ulster Constabulary base in Lurgan, 20 miles southwest of Belfast.

Supporters of the mainly Roman Catholic IRA identified Marshall as a member of its legal political wing, Sinn Fein. He was imprisoned from 1976 to 1982 for terrorist offenses, police said.

Two survivors of the Wednesday night shooting accused police of cooperating with the gunmen.

Tony McCaughey, 31, and Colm Duffy, 22, said they were under police surveillance when the gunmen attacked.

The Royal Ulster Constabulary denied the allegations of collusion with the killers.

The three men were out on bail after being charged with illegal possession of ammunition. One of the bail conditions was that the three had to report to the Lurgan police station twice a week on Saturdays and Wednesdays.

McCaughey and Duffy said the bail conditions were known only by the police and their lawyers.

''Neither of us will be reporting back to the station,'' McCaughey said. ''We would prefer to go back to prison than go back to the RUC station.''

Duffy said a car followed them to the police station Wednesday night and was seen again just after the attack. He said it was an unmarked police car.

''We want Stevens to carry out the investigation, and to come up with some answers to who owned it,'' Duffy said. ''We have absolutely no qualms about talking to Stevens.''

John Stevens, deputy chief constable of Cambridgeshire, was sent to Northern Ireland in September to investigate a series of leaks from the Northern Ireland police force of lists of IRA suspects.

The leaks stirred a furor in the province, the implication being that secret intelligence is falling into the hands of Protestant gangs and helping them choose assassination targets.

Irish Foreign Minister Gerry Collins on Thursday called for an investigation into the new charges of collusion.

Duffy said soon after leaving the police station Wednesday night, two masked men armed with rifles pulled up in a red Rover car and fired 40 shots.

Police said Marshall was killed instantly. McCaughey and Duffy were unhurt.

The British domestic press agency, Press Association, quoted unidentified sources as saying Marshall had been warned by police recently that he was on a Protestant paramilitary hit list.

The IRA is fighting British rule in Northern Ireland. It seeks to unite the predominantly Protestant province with the 95 percent Catholic Republic of Ireland under socialist rule.