The closure of Everest's northeast ridge came after China told tourist agencies in Tibet to cancel all tours until April and stopped issuing entrance permits for Tibet to foreigners.

Tensions in Tibet are running high ahead of the anniversary of the Dalai Lama's flight into exile on March 10. Many Tibetans have chosen not to celebrate Tibetan New Year, or Losar, today (weds) to silently protest Chinese rule.

China's move to close off Tibet will ensure a news black-out in case of any repeat of the violence that broke out last March. Large squads of riot police have already been spotted by reporters in Tibetan areas of the surrounding provinces.