In a pre-dawn swoop, police on Monday arrested five foreign nationals under Britain's sweeping anti-terrorism laws, citing national security concerns.
They were arrested at one London address and will be held pending deportation, a spokeswoman at the Home Office said.
She, however, declined to disclose their nationality or any other details of the detainees.
"The immigration service detained five individuals in accordance with the Home Secretary's powers to deport individuals whose presence in the UK is not conducive to the public good for reasons of national security," she said.
The Immigration Act 1971 gives powers to deport individuals and detain them pending deportation.
The five foreign nationals have been detained on this basis and they will be held till they are deported, the spokeswoman said.
The raid is the latest in a series of such detentions following the serial bomb attacks on London in July in which 52 were killed.
The Government detained 10 people on August 11, including the alleged spiritual leader of Al-Qaeda in Europe and seven Algerian men on September 15, saying they were a threat to the national security.