The 25-year-old from Bedfordshire was taken to a London police station, the Metropolitan Police Service said in a statement. Two properties are being searched in the county, north of London.

British police said last week they are running an “exceptionally high” number of terror probes related to the Islamist uprising in Syria and Iraq. Bernard Hogan-Howe, the Metropolitan Police commissioner, said more than 500 Britons had gone to join the fighting, at a rate of about five a week, the Press Association reported yesterday.

The U.K. terror alert was raised to “severe” in August amid concerns those fighters would return home and carry out domestic attacks. Thames Valley Police, west of London said last week that they arrested six people in connection with activities in other countries.

Separately, last week four men who allegedly took an oath to Islamic State were charged in a terrorist plot to kill police officers and soldiers in London.

To contact the reporter on this story: Kit Chellel in London at [email protected] To contact the editors responsible for this story: Anthony Aarons at [email protected] Eddie Buckle