British police have made a third arrest in connection with a tube attack in Parsons Green, London, that injured 30 people.
Tuesday's arrest, of a 25-year-old man, was made in Newport, Wales, they said in a statement.
Two other men who have been detained in connection with the attack remain in police custody.
"This continues to be a fast-moving investigation. A significant amount of activity has taken place since the attack on Friday," said Dean Haydon, head of the Metropolitan Police's Counter Terrorism Command.
"We now have three men in custody and searches are continuing at four addresses. Detectives are carrying out extensive inquiries to determine the full facts behind the attack."
The home-made bomb went off on Friday during the morning rush hour on a packed train at Parsons Green underground station, engulfing the carriage in flames.
On Saturday, police arrested a 18-year-old man in Dover, southeast England, and a 21-year-old in west London over the attack.
A total of 36 people have been killed in Britain this year in militant attacks.