China's repression of Tibetans is getting worse, in some ways due to the Olympics, activists say, adding that they are planning demonstrations in Beijing during the Games despite zero tolerance and a massive security presence.

The New York-based group Students for a Free Tibet also said on Friday that a "surprising" number of athletes and Olympic hopefuls had responded to an online campaign to show support for the Tibet issue when in Beijing.

"The situation inside Tibet remains extremely tense ... the repression Tibetans are living under is far from over, it's in some ways getting worse," said Lhadon Tethong, executive director of Students for a Free Tibet, said in a teleconference.

The Chinese government says followers of the Dalai Lama, Tibet's exiled Buddhist leader, fomented protests and riots across the mountain region in March in a bid to derail the Olympics, which start in a week.

The Dalai Lama rejects accusations that he is behind the unrest, but since the rash of demonstrations security forces have mounted a sweeping crackdown in Tibet and neighbouring provinces.

On Friday, Zhang Qingli, the hardline Communist leader of Tibet, said Tibet had returned to normal in terms of social order, but "it's still a tough task to maintain peace in the region".

"Troops in Tibet should always be prepared for possible emergencies, to safeguard the national defence security and region's peaceful development," the state news agency Xinhua quoted him as saying at a celebration of the anniversary of the founding of the People's Liberation Army.

The Chinese government was using the Olympics to "legitimise their occupation of Tibet", Lhadon Tethong said.

"We are hearing reports of Tibetans across Tibet and in China itself who are facing increased and severe restrictions and harassment in the lead up to the Games."

The repression in Buddhist monasteries across the region was some of the harshest in decades, she said, adding over 1,000 monks from key monasteries were missing and reportedly being held in camps until after the Olympics.

Students for a Free Tibet said it was planning protests at Chinese embassies and consulates and other public areas in cities around the world, but declined to give details of what was planned for Beijing due to security concerns.

The Chinese government says it will allow pre-approved protests in three Beijing parks during the Games, but it is widely expected that a wide variety of would-be protesters, including those pushing for independence or autonomy in Tibet, will not be allowed.