A man was arrested in central England on Thursday under Britain's 2000 terrorism act, police said.
The arrest in the city of Birmingham came a day after eight British suspects appeared in court charged in a plot linked to security alerts at financial targets in New York, New Jersey and Washington.
An anti-terror police spokesman said Thursday's arrest was not related to this operation.
The man, 19, lived in the Sellyoak area of Birmingham, Britain's second-largest city.
"A 19-year-old man was arrested under the terrorism act 2000 today," said police spokeswoman Daljinder Mattu. He was being held in custody and was due to be questioned by police.
Mattu said another two men, aged 24 and 36, were arrested in the same area "in relation to immigration matters."
The nationalities of the three men were not immediately available.
Britain has arrested more than 600 terrorist suspects since the Sept. 11, 2001, attacks but has charged fewer than 100 and convicted only 15 of terrorism offences.
8 charged with conspiracy to murder, mayhem
The eight suspects who appeared in court at a high security prison on Wednesday have been charged with conspiracy to commit murder and to use explosives, chemicals or radioactive materials to cause disruption, fear or injury.
None entered a plea, and were ordered held in custody until a court appearance next week.
Among the defendants was an alleged senior al-Qaida operative also charged with scouting prominent financial targets in the United States, including the New York Stock Exchange, the World Bank and the International Monetary Fund.
Prosecution lawyer Sue Hemming said all eight suspects were motivated by "a strong and deeply held ideology" and were willing to carry out extreme acts.
Hemming said police have around a hundred computers and thousands of files to examine as part of what looms as a long and complex investigation.
"We've only hit the tip of the iceberg as far as a lot of this evidence goes," she told the high security Belmarsh Court in south London.
Men linked to Pakistan arrests
The charges, filed Tuesday after two weeks of interrogation, for the first time officially linked the Aug. 3 arrests across Britain and a series of arrests last month in Pakistan to the Aug. 1 terrorism alerts surrounding the New York Stock Exchange and Citigroup Inc. headquarters, the International Monetary Fund and the World Bank buildings in Washington, and the Prudential Financial Inc. building in Newark, N.J.
One defendant, Dhiren Barot, 32, was charged with possessing reconnaissance plans for the New York Stock Exchange, the International Monetary Fund, the Citigroup building and the Prudential building; and with possession of notebooks containing information on explosives, poisons, chemicals and related matters.
A U.S. official in Washington, speaking to The Associated Press on condition of anonymity, said Barot is the suspected al-Qaida figure previously identified as Abu Eisa al-Hindi or Abu Musa al-Hindi.
Following the Aug. 1 terror alert involving those buildings and the World Bank in Washington, the U.S. government acknowledged it had no evidence of plans for imminent attacks. The charges specified that Barot had the plans as early as Feb. 19, 2001.
U.S. Attorney General John Ashcroft said Tuesday that federal authorities were considering whether to press charges in the United States against the men and to seek their extradition.