Five Americans expelled from China after staging an illegal protest at a Mount Everest base camp in Tibet last week have vowed to step up their campaign for a "free Tibet." China has now lodged an official protest with the U-S over the protest, in which the Americans called for Tibetan independence.

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Presenter/Interviewer: Liam Cochrane
Speakers: Tenzin Dorjee, the deputy director of Students for a Free Tibet

DORJEE: And behind us you can see the majestic mountain, the highest mountain in the world. It belongs to the Tibetan people. This is Tibet. I am a Tibetan and this is my land. The Chinese government has no right to be here.

COCHRANE: It was these feisty words at the base of Mount Everest that landed Tenzin Dorjee and four other American activists in detention for two-and-half days. The US-based advocacy group, Students for a Free Tibet organized protest - they unfurled a banner which parodied the Beijing Olympics slogan, saying "One world, one dream, free Tibet 2008".

It wasn't long before they were spotted by Chinese border guards and taken into custody. Speaking from a hotel in Kathmandu a few days after being expelled from China, Mr Dorjee described their 55 hour detention.

DORJEE: They put us through three different rounds of interrogation... They took each of us into a separate small room where there was one man who was interrogating us in English, one man who was taking notes of everything we were saying, and then two men who were saying close enough to us holding machine guns.

COCHRANE: The five activists were deprived of food for most of their first day, but on the second day were taken to a fancy Chinese restaurant to have breakfast with officials, as people took photos of them eating well.

None of the protesters were physically harmed in custody, but one of the female activists, Shannon Service, said she was threatened by the woman questioning her. Ms Service was placed in a cold room and told that if she didn't cooperate, she'd have to spend the night there.

DORJEE: Just the temperature of that room was so cold that she would not have made it out, you know, in the morning; just because it was so cold. And she was also told, we will keep you in this room tonight and harm will come to you.' That was what the interrogator said to Shannon. And at that point Shannon felt really explicitly threatened and she asked back, 'Did you just threaten me?' and the response was, 'Yes'.

COCHRANE: At this point, Shannon Service refused to speak until she was allowed to contact the US Consulate in China and was taken to wait in a car outside.

DORJEE: One of the official men, one of the officials came next to the car, standing outside the car and he gestured his hand in the shape of a gun and pulled the trigger at her head, from outside. And at that point Shannon was really really afraid and wasn't sure how to react and she really thought that it was going to be very serious, they way the handled us, and they could do anything, she really thought they were capable of doing anything.

COCHRANE: The five activists knew their American citizenship would give them some protection, but say that wouldn't have been the case for Tibetans if they'd pulled a similar stunt.

Tenzin Dorjee had pretended to only understand English, but was secretly listening in to what officials were saying in Tibetan and Chinese. After Shannon Service demanded to speak to the US Consulate, her interrogator sat next to Mr Dorjee in a car and he overheard her conversation with a colleague.

DORJEE: What she said was, "Because of the fact that she's American, I'm not really able to do what I want to do. And she said, "If she hadn't been American I would just really like to just slap her face in and put her in jail."

COCHRANE: Eventually, the five were expelled from China without being charged. Radio Australia contacted the Chinese embassy in Kathmandu, but the press spokesman wouldn't comment, saying they had not heard about the incident.

However, a spokesman for China's Foreign Ministry told AFP news agency in Beijing that foreign visitors to China should not get involved in activities regarding what he called "the sovereignty or unity of China."