Miranda had been refused access to a lawyer and officials had taken his laptop and mobile phone, Greenwald added.

The British interior ministry did not immediately comment on Miranda's detention, saying it was a police matter.

But authorities were under increasing pressure to explain why he had been held, with Brazil expressing "grave concern" that one of its citizens had been apparently "held incommunicado "at the airport.

Keith Vaz, chairman of the British parliament's home affairs committee, said he was writing to the police to demand an explanation, describing Miranda's detention as "extraordinary".

"They may have a perfectly reasonable explanation," he told BBC radio.

"But ... if we are going to use the (Terrorism) Act in this way, for those issues that are not related to terrorism, then at least we need to know."

About the broadcaster:

Lance Crayon is a videographer and editor with China Daily. Since living in Beijing he has worked for China Radio International (CRI) and Global Times. Before moving to China he worked in the film industry in Los Angeles as a talent agent and producer. He has a B.A. in English from the University of Texas at Arlington.

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