Six men were being questioned at police stations in London and Liverpool last night in connection with the dissident Irish republican bombing campaign in Britain.
The arrests are the first to take place during an Anti-Terrorist Branch and Intelligence Service investigation into seven terrorist incidents in London and Birmingham in the past 18 months blamed on the so-called "Real IRA".
In a follow up operation last night police carried out several controlled explosions at a farm at West Ardsley, West Yorkshire. No further arrests were made. Scotland Yard said a number of neighbours were evacuated and that detectives would continue searching the farm this morning.
Five suspects are being questioned at a central London police station and the sixth is being held in Liverpool following a "lengthy" investigation into dissident republican activity in Britain. The men were arrested by officers from Scotland Yard's Anti-Terrorist Branch, supported by specialist firearms teams, raided on during separate raids on addresses in London and Liverpool shortly before 6 a.m.
They are believed to be Irish, but it is not clear whether they are from the Republic or Northern Ireland.
Several addresses in London and Liverpool were still being searched yesterday and the development in the investigation comes less than two weeks after a car bomb packed with up to 30kg of home-made explosives partially detonated in Birmingham city centre.
Anti-terrorist police blamed the "Real IRA" for planting the device, insisting if it had fully exploded it would have caused substantial loss of life, and have pointed to "Real IRA" involvement in several terrorist incidents in London since June 2000.
These include a car bomb explosion in Ealing in August, a car bomb outside BBC TV headquarters in west London in March and a rocket attack on MI6 headquarters last September.
Deputy Assistant Commissioner and head of the Anti-Terrorist Branch, Mr Alan Fry, said the arrests were the result of a co-ordinated police effort to track down terrorists. "Those in custody are being questioned in connection with the current bombing campaign on the UK mainland," Mr Fry said
The six, aged 20 to 40, were arrested under the Terrorism Act and can be held in police custody without charge for 48 hours, after which police must seek permission from a magistrate if they want to detain them for up to five days. The men must be released or charged within seven days.