British officials warned today of a possible Christmas bombing campaign by Irish Republican Army terrorists after two bombs exploded outside a British Army reserve barracks in London last night, slightly injuring five people. An unsuccessful attempt to shoot British European Economic Community commissioner Christopher Tugendhat, as he left his home in Brussels this morning to go to work, added to official British concern.

Although no one has claimed responsibility for either attack, London police sources said the devices used in last night's bombing are like those used by the IRA. And in an interview today a Scotland Yard official said, "We're all but certain the IRA carried out the bombing. There are a number of IRA men now in London and we are taking measures to prevent more violence."

There is less evidence to link the IRA with the attempt to shoot Tugendhat this morning in Brussels, but British officials said today that the IRA was probably responsible for killing the British ambassador to The Hague last year and cited several attacks on British soldiers serving in West Germany. Belgian police are still investigating the shooting by two men in a car that immediately sped away.

British police antiterrorist experts said further IRA attacks against English targets can be expected as tension rises over the possible deaths of IRA prisoners on hunger strike in Northern Ireland in a campaign to gain special treatment as "prisoners of war."

The IRA has threatened a "campaign of retribution" if any of the hunger strikers dies, which British medical experts say could happen within the next two weeks.

London police appealed for increased security, asking shops, restaurants and prominent people to be especially vigilant and calling for information on any boarders with a strong Irish accent.