Politicians in Britain are calling on police at Heathrow airport to explain why they detained the Brazilian partner of an American journalist for nine hours under terror laws.
David Miranda is the partner of Glen Greenwald, a Guardian reporter who published documents leaked by a former US intelligence analyst who has since been granted asylum in Russia.
Mr Miranda was on his way to Rio de Janeiro from Berlin.
Mr Greenwald said officials were trying to intimidate him through his partner.
The Guardian said Mr Miranda, 28, often assists Greenwald with his work. He is not an employee of the newspaper but it had paid for his flights.
Mr Miranda said he was questioned under schedule 7 of the Terrorism Act 2000 by six agents at Heathrow who confiscated his electronic equipment.
Brazil says it is gravely concerned by the unjustified detention of one of its citizens.