Police have arrested a 21-year-old man in London on suspicion of attempting to join Isis in Syria.
A spokesperson for the Metropolitan Police said counter-terrorism detectives believed the man was planning to travel to the country "for a terrorist purpose".
He was arrested in central London shortly after midday on Thursday and remain in custody at a local police station.
"The 21-year-old was arrested on suspicion of being involved in the commission, preparation of instigation of acts of terrorism under Section 40 of the Terrorism Act 2000," a spokesperson for Scotland Yard said.
"Searches are being carried out at two London addresses and an address in Birmingham as part of this investigation."
It came after America's intelligence chief said there was evidence that Isis terror cells in the UK and other European countries were plotting further attacks in the wake of the Brussels and Paris massacres.
James Clapper, the Director of National Intelligence, said organised groups of militants are active in Germany, England and Italy.
He said Isis cells embedded in Europe were “fanatics”, with a high level of security in communications that leaves security services struggling to get more than a "snapshot" of their plans.
“We don’t have the total picture all the time – if we did, then the plots would easily be thwarted,” Mr Clapper added.
Several terror arrests have been made in the UK since the start of this year, including four men and a woman from Birmingham who were detained in a joint operation with French and Belgian agencies earlier this month.
