Two suspected Basque terrorists have been arrested by armed police in London, officials said.
Antonio Troitino Arranz and Ignacio Leron Sanchez, described as senior members of ETA by the Spanish interior ministry, were held in connection with alleged terrorist offences in Spain.
Both men were held under the Extradition Act after being arrested at a residential address in Hounslow, west London, at about 4am, police said.
Arranz, 55, and Sanchez, 39, were arrested by officers from Scotland Yard's counter terrorism command, supported by armed police and officers from the force's extradition unit.
The Spanish interior ministry added that both men were senior figures in ETA and were wanted in connection with a series of terrorist acts in Spain.
Searches at two addresses in west London are under way and the men are being held at a central London police station.
The arrests are not linked to the Olympics, which are less than a month away, police said.
A 38-year-old woman was arrested at the same address for alleged fraud offences and two other men were held over alleged immigration offences.
The arrests come after a suspected Basque terrorist lost his application to appeal to the Supreme Court against extradition to Spain where he is accused of the attempted assassination of the Spanish king.
Lawyers for Eneko Gogeaskoetxea Arronategui, 44, argued that his case raised questions of law of public importance that should be considered by the highest court in the land. But the High Court in London rejected the submission on Wednesday and refused permission for a last-ditch appeal to the Supreme Court.