A government official, who spoke on condition of anonymity, confirmed that the Palestinian cleric described by British officials as Osama bin Laden's "spiritual ambassador in Europe," was in custody.
"People have been whisked off to prison and we are being denied access to them," said Abu Qatada's lawyer Gareth Peirce. "Now it's suddenly fine to deport people who for years the government has said it was unsafe to do so. It's quite extraordinary."
Prime Minister Tony Blair has been under pressure to take tough action against foreign nationals who incite terrorism, after four bombers killed themselves and 52 other people in attacks on London's transport system on 7 July.
The government announced plans last week to deport those it believes are inciting or glorifying attacks and has signed agreements with some countries to return them, including Jordan.
Home Secretary Charles Clarke said the presence of the 10 foreign nationals was "not conducive to the public good".
"We now have good reason to believe that we can get necessary assurances from the countries to which we will return the deportees so that they will not be subject to torture or ill-treatment," Clarke said in a statement.
The detentions came the same day 10 people were due to appear in court under anti-terrorism laws over a failed attempt to bomb London two weeks after the first attack.
Clarke said the 10 people
arrested threatened security
All have been charged with keeping information from police hunting suspects.
Britain has said in court papers that Qatada, 44, is a "truly dangerous individual ... at the centre in the United Kingdom of terrorist activities associated with al-Qaida".
He was sentenced in Jordan to life imprisonment in absentia for involvement in terrorist attacks there in 1998.
Clarke said the men were detained on Thursday by immigration officers backed by the police under existing powers available to him under the UK's Immigration Act, and would be held in prison.
Britain rushed through laws after the 11 September 2001, attacks on the United States, giving police the power to hold
foreign terrorism suspects indefinitely without charge or trial.
After the UK's top court ruled this illegal, the powers were replaced with new legislation which allowed the government to impose restrictions on suspects including house arrest.
Britain is holding 10 people under these "control orders" including Qatada. The Home Office said some of those being deported were being held under control orders.
Clamour for the government to take action has grown in the last week after some foreign Muslim preachers condoned the July attacks on London.