An officer with the Police Service of Northern Ireland has been killed in a town southwest of Belfast, police said Monday.

The officer was shot in the head while sitting in his patrol car in the religiously divided town of Craigavon, about 40 kilometres southwest of Belfast, police said.

The shooting came two days after two gunmen killed two British soldiers at the entrance of an army base in Antrim, 25 kilometres northwest of Belfast. It was the first slaying of British security forces in Northern Ireland in 12 years.

Four others, including two soldiers, were wounded in the weekend attack. The Real IRA republican splinter group claimed responsibility for the Saturday shooting, but no one has come forward in the latest attack.

Basil McCrea, a Protestant politician, said he had no doubt that IRA dissidents also committed Monday's attack. He said he expected the Real IRA to mount another attack, "but we didn't think it would be so soon."

Earlier on Monday, British Prime Minister Gordon Brown vowed that the killers responsible for the Saturday deaths will be found and brought to justice.

The two gunmen and their getaway driver "have got to be hunted down and brought to justice as quickly as possible," Brown said.

Brown also met with Northern Ireland's political leaders in Belfast on Monday in an effort to ensure the attack would not reverse progress made since the Good Friday peace deal of 1998, which helped reduce the sectarian violence in which more than 3,600 people died since the 1960s.

Brown said the attack would not be allowed to undermine the Catholic-Protestant government at the heart of the peace process.

The Real IRA splinter group is continuing to pursue the goal of forcing Northern Ireland out of the United Kingdom and into the Republic of Ireland, a goal that has been abandoned by the mainstream IRA.

The group carried out the deadliest single bombing during Northern Ireland's sectarian violence in August 1998 when 29 people were killed in Omagh.

A report by the Independent Monitoring Commission said the Real IRA and another dissident group, the Continuity IRA, have recently stepped up their activity.

With files by the Associated Press