Five foreign activists have been detained in Beijing after they unfurled a "Free Tibet" banner at the new headquarters of state-run China Central Television.

The incident comes as the International Olympic Committee (IOC) urged China to allow foreign reporters at the games to report freely after police allegedly roughed up a British journalist trying to cover a Tibet protest.

Police said they mistook him for a protester.

On Friday three Americans, a Briton and a Canadian - all members of the New York-based Students for a Free Tibet group - scaled and hung the black-and-white banner from the Beijing building still under construction before police detained them.

Television footage showed them draped in Tibetan nationalist flags and helmets dangling from ropes from the new headquarters.

Protest platform

Pro-Tibet and other activists have sought to use the Beijing Olympics to draw attention to China's rights record and religious restrictions.

Following the incident with the British journalist, an IOC spokeswoman said the committee disapproved of "any attempts to hinder a journalist who is going about doing his job seemingly within the rules".

"This, we hope, has been addressed. We don't want to see this happening again," Giselle Davies said.

Activists have also complained that protest zones designated by games organisers were set up as a way to catch dissidents, and not to let them speak out.

Police have detained at least one person who applied to hold a demonstration in one of three designated protest parks.

"It's clear to us that the protest zones are just a cynical public relations ploy on the part of the Chinese authorities," Lhadon Tethong, of Students for a Free Tibet, said.

"Sadly, I think the protest zones are just a trap at some level."

On Thursday, Wang Wei, the Beijing organising committee vice-president, in suggesting that critics were nitpicking, called the protest parks "one step further for China to open up and I think it's [a] very good gesture".