A bomb blew up Saturday on a road near the Irish border and killed three members of a family headed home after a vacation in the United States, police said.

The outlawed Irish Republican Army, fighting to end British rule in Northern Ireland, admitted it was their bomb but that it detonated prematurely and was meant for British soldiers, not civilians.The blast blew a crater in the road and left bodies and luggage scattered on the main road between Dublin and Belfast, witnesses said.

Killed in the explosion were Robert James Hanna and Maureen Patricia Hanna, both 44, and their son David, 6.

They were driving to their home in Hillsborough, 12 miles south of Belfast, when the explosion occurred at 10 a.m. near Newry, about a mile from the Irish border, police said. It was not immediately known where they vacationed in the United States.

Three people in nearby cars were slightly injured.

The explosion brought to 21 the number of people killed in explosions in Northern Ireland this year, police said.

The IRA is fighting to drive the British out of the predominantly Protestant province and unite it with the Roman Catholic Irish Republic.

The IRA issued conflicting statements explaining the bombing.

In a statement issued to journalists in Northern Ireland, the South Armagh Brigade of the IRA said the Hannas were the "unfortunate victims of mistaken identity." It said the attack was a carefully planned military operation that ended in "tragic and unfortunate circumstances."

Officials speculated the IRA mistook the family's jeep for a Land Rover used by British security forces.