Three men arrested on suspicion of terror offenses are linked to an investigation into threats to kill British Prime Minister Gordon Brown, police sources have confirmed.
Although there was no firm plot, an extremist jihad Web site had called in January for Brown's death.
The Internet hosts many sites from groups and individuals claiming allegiance to Al Qaeda and Usama bin Laden.
It routinely issues warnings and threats to political leaders in the U.K. and the U.S. over the West's involvement in the Middle East.
The three suspects, aged 21, 22 and 23, and from Blackburn, Lancashire, were all arrested on Aug. 14 under the Terrorism Act 2006.
Two were detained at Manchester Airport as they were about to board a flight to Finland; the third was arrested in Accrington, Lancashire.
Counter-terrorist officers from Greater Manchester and Lancashire have flown to Scandinavia to continue their investigations.
Detectives have been granted up to next Thursday to hold the suspects, when they will have to charge them, release them or seek an extension to their custody.
The sweep was said to be the culmination of a counter-terrorism operation between Lancashire Police and Greater Manchester Police's Counter Terrorism Unit (CTU).
Neighbours described the suspects as "normal everyday lads."
One man who lives in Percival Street, where two of the men lived, said: "You don't expect it on your doorstep but that's life. It could happen anywhere."