The Olympics have so far failed to catalyse reform in China and pledges to improve human rights before the Games look disingenuous after a string of violations in Beijing and a crackdown in Tibet, Amnesty International said.

The International Olympic Committee (IOC), foreign leaders and overseas companies engaging with China could appear complicit if they failed to speak out about the rights violations, the London-based watchdog said on Wednesday as the volume of criticism of China grows around the world.

Beijing signed up for the Games hoping they would showcase the country's progress and national unity, but the Olympics year so far has seen pressure mount, chiefly over China's policy towards Sudan and Myanmar and its human rights record, most recently in Tibet.

In and around Beijing, Chinese authorities have silenced and imprisoned human rights activists in a pre-Olympics "clean up", Amnesty said.

Amnesty, which introduced a bandana-wearing monkey mascot to head its "Uncensor China" campaign, also said the crackdown on a rash of demonstrations in and around Tibet in recent weeks had led to "serious human rights violations".

"These actions cast doubt on whether the Chinese authorities are really serious about their commitment to improve human rights in the run up to the Olympics," Irene Khan, Secretary General of Amnesty International, said in a statement.

"The Olympic Games have so far failed to act as a catalyst for reform. Unless urgent steps are taken to redress the situation, a positive human rights legacy for the Beijing Olympics looks increasingly beyond reach."

Days of monk-led marches in Tibet's capital Lhasa devolved into a citywide riot on March 14 that saw Chinese shops trashed and burned and cars overturned. The government says the violence killed 18 civilians and at least one police officer. The Tibet government-in-exile says around 140 people died.

AMNESTY "BIASED"

Human Rights Watch fired another barrage on Tuesday, accusing the IOC of operating in a moral void, undermining human rights in China and flouting the spirit and letter of the Olympic Charter.

Australian IOC member Kevan Gosper fired back, saying the committee was not an activist group or a government.

"We can talk quietly behind the scenes but it's really up to governments to deal with matters of human rights and the NGOs concerned," he said. "Our job is to deliver a great Olympic Games for the athletes of the world and we must keep our focus on that."

In a 2001 pitch for the Games, Beijing Olympic organising chief Liu Qi said the event would "benefit the further development of our human rights cause".

The ruling Communist Party's concept of human rights emphasises basic necessities for the entire populace, like food, clothing and shelter, rather than individual freedoms, which are frequently subjugated.

Chinese Foreign Ministry spokeswoman Jiang Yu said on Tuesday that Amnesty was biased and its report predictable.

"Anyone planning to use the Olympics to threaten China, or planning to put pressure on China, has miscalculated," Jiang told a news conference.

Introducing its campaign mascot "Nu Wa", which means angry young boy, Amnesty said his job was to counter the "Fuwa", the five official mascots of the Beijing Olympics.

"Their overly happy and cute demeanour defies the worsening human rights situation inside China today, Amnesty said. "Nu Wa wants to set the record straight."