RIO DE JANEIRO (AP) -- An American journalist who has written stories based on documents leaked by former National Security Agency contractor Edward Snowden said Monday he'll publish with more fervor after British authorities detained his partner.
London police detained David Miranda under anti-terror legislation as he arrived at Heathrow Airport in London airport Sunday. Miranda, who is in a civil union with reporter Glenn Greenwald, arrived Monday in Rio de Janeiro, where he lives with the journalist.
A defiant Greenwald, who reports for the Guardian newspaper in Britain, promised he was going "to write much more aggressively than before" about government snooping.
"I'm going to publish many more things about England, as well," he said in Portuguese at Rio's international airport when Miranda arrived. "I have many documents about England's espionage system, and now my focus will be there, too. I think they'll regret what they've done."
In Washington, White House spokesman Josh Earnest said the U.S. government was tipped off by British counterparts that Miranda would be detained, but the U.S. had not requested the action. The spokesman didn't respond to a question about whether U.S. officials may have discouraged British officials from stopping Miranda.
The Brazilian government objected to Miranda's detention, saying it wasn't based on any real threat.
London's Metropolitan Police defended the decision to detain Miranda, saying the examination was both "necessary and proportionate."
The statement said an attorney had been offered to Miranda, but the Brazilian later told the Guardian in an interview that he refused to use the lawyer out of fear of the British government.
Miranda told the Guardian that agents questioning him "were threatening me all the time and saying I would be put in jail if I didn't cooperate."
Miranda said he was seized almost as soon as his plane landed at Heathrow. "There was an announcement on the plane that everyone had to show their passports. The minute I stepped out of the plane they took me away," he said.
Agents confiscated Miranda's computer, external hard drive, cellphone, DVDs, memory sticks and some paper documents.
In London, a British lawmaker called for police to explain why Miranda was detained and why it took nearly nine hours to question him.
Miranda was held for nearly the maximum time that British authorities are allowed to detain individuals under the Terrorism Act's Schedule 7, which authorizes security agencies to stop and question people at borders.
Keith Vaz, chairman of Parliament's Home Affairs Select Committee, told the BBC that "you have a complaint from Mr. Greenwald and the Brazilian government -- they indeed have said they are concerned at the use of terrorism legislation for something that does not appear to relate to terrorism. So it needs to be clarified, and clarified quickly."
Vaz said it was "extraordinary" that police knew that Miranda was Greenwald's partner and that the authorities were targeting partners of people involved in Snowden's disclosures.
The case drew the ire of watchdog groups.
"It's incredible that Miranda was considered to be a terrorist suspect," said David Mepham, the British director at Human Rights Watch. "On the contrary, his detention looks intended to intimidate Greenwald and other journalists who report on surveillance abuses."
Britain's laws are not unique. U.S. customs officials can search the electronic devices of anyone entering the U.S. without a search warrant. According to a 2011 internal Homeland Security Department report, officers at the border can search the devices and in some cases hold on to them for weeks or months. The DHS has said such searches help law enforcement detect child pornographers or terrorists.
Greenwald has written about NSA surveillance programs based on files disclosed by Snowden, who now has temporary asylum in Russia. The Obama administration wants Snowden sent back to the United States to be tried for the leaks.
Miranda, a 28-year-old university student, was traveling home to Brazil after visiting Germany, where he met with Laura Poitras, a U.S. filmmaker who has worked with Greenwald on the NSA stories.
A spokesman for Prime Minister David Cameron said that "Schedule 7 forms an essential part of the U.K.'s border security arrangements," but added that it was for the police to decide "when it is necessary and proportionate to use these powers."
Brazil's Foreign Minister Antonio Patriota and his British counterpart, William Hague, spoke by phone Monday, the British Embassy in Brasilia said in a statement.
"They agreed that Brazilian and U.K. officials will remain in contact on this issue. This remains an operational matter for the Metropolitan Police," British Ambassador Alex Ellis said in an emailed statement.