British authorities used anti-terrorism laws on Sunday to detain David Miranda, partner of U.S. journalist Glenn Greenwald, as he passed through London's Heathrow airport.  RIO DE JANEIRO The journalist who first published secrets leaked by fugitive former U.S. intelligence agency contractor Edward Snowden vowed on Monday to publish more documents and said Britain will "regret" detaining his partner for nine hours. Miranda told reporters that six British agents questioned him about all aspects of his life during his detention in a room at Heathrow airport. Brazil's foreign minister Antonio Patriota said he would call his UK counterpart William Hague to tell him the detention of Mr Miranda - a Brazilian national - was "not justifiable" and ask him to ensure it "won't happen again". Brazil complained about the "unjustified" detention of Miranda under a British law used for suspects of terrorism. The White House said on Monday that U.S. officials did not ask the British government to question Greenwald's partner, though British authorities did give their U.S. counterparts a "heads up" before detaining Miranda. "I have lots of documents about the way the secret services operate in England," he said. I think they will be sorry for what they did," Greenwald, speaking in Portuguese, told reporters at Rio de Janeiro's airport where he met Miranda upon his return to Brazil. 'Extraordinary' 
 
 Mr Snowden, who has been granted temporary asylum in Russia, leaked details of extensive internet and phone surveillance by American intelligence services.
– Well, now the UK has gone and gotten itself on Glenn Greenwald's bad list. The Guardian journalist behind the Edward Snowden-NSA leaks story told reporters that after his partner was detained for nine hours at London's Heathrow airport, he plans to be "far more aggressive" in his reporting, Reuters reports. "I am going to publish things on England, too. I have many documents on England's spy system. I think they will be sorry for what they did," he said. Greenwald was at the Rio de Janeiro airport at the time to meet partner David Miranda upon his return to Brazil, where they both live. Brazil's government released a statement calling Miranda's detention unjustified, the Guardian also wants answers, and now even lawmakers in the UK are calling for an explanation from police as to why Miranda was held, the BBC reports. The Independent Reviewer of Terrorism Legislation says it's rare for anyone to be held for so long under schedule 7 of the Terrorism Act 2000, which allows police to detain someone at an airport for as long as nine hours to question them about links to terrorism. But "they never asked him about a single question at all about terrorism or anything relating to a terrorist organization," Greenwald says. "They spent the entire day asking about the reporting I was doing and other Guardian journalists were doing on the NSA stories."