Gordon Brown yesterday vowed that no stone would be left unturned in hunting down the "evil" killers of the policeman and two soldiers gunned down earlier this week.

The Prime Minister led the Westminster Parliament in expressing sympathy to the victims and their families and praising the resolve of local people in standing up to the terrorists.

He said: "Out of tragedy we are seeing a unity, which shows the determination that, while a few murderers may try to disrupt the process, the people of Northern Ireland want not only to see justice done but to send a message that the political process is here to stay and is working."

And he vowed: "We will do everything in our power to track down these killers."

Conservative leader David Cameron branded the perpetrators "callous killers", who were "capable of shooting men in cold blood and standing over their wounded bodies and murdering them".

He added: "The important thing is that everyone works with the police so these killers can be found, caught, charged and convicted."

Nick Clegg, the LibDem leader, said the violence of the killers "must not, will not, divide the people of Northern Ireland; instead it will strengthen their resolve to live their lives in peace".

Labour's Peter Hain, a former Northern Ireland Secretary, praised Republican leaders for their "unequivocal" condemnation of the shootings and noted: "The people of Northern Ireland want the political process to be both maintained and strengthened."

David Simpson, the Demo- cratic Unionist MP for Upper Bann - in whose constituency murdered policeman Stephen Carroll lived - branded the murderers as "vermin".

He asked Mr Brown to ensure Sir Hugh Orde, Northern Ireland's Chief Constable, had the resources he needed to prevent the terrorists from taking the area "back into the 35 years of hell on earth we have come through".

Mark Durkan, leader of the Nationalist SDLP, noted how the young people the terrorists were seeking to recruit "know that the real patriots serving the peace of the new Ireland were Constable Carroll and his colleagues, who went to answer the call of a woman in distress, not those who brutally murdered him".