British police are questioning a woman arrested in connection with the activities of the "Real IRA" there last year.
The 35-year-old woman was arrested during a raid on a house in north London.
She is being held at a central London police station under the Terrorism Act 2000, a spokesman says.
Two men are set to stand trial at the Old Bailey in May over bomb blasts in London and Birmingham last year.
Mr Noel Maguire (32) is accused of causing explosions at Ealing, on August 3rd last year and at the BBC in west London, on March 3rd last year.
Mr Robert Hulme (22) is accused of causing an explosion in Birmingham on November 3rd, possessing explosives and firearms offences.
They have both been charged with conspiracy to cause explosions to endanger life.
PA