The United States on Sunday urged China to release eight US citizens who were sentenced last week to 10 days in detention for their role in a series of protests in support of Tibetan independence.

US envoy to China Clark T Randt raised the issue of the detentions with Chinese officials on Saturday and called for the immediate release of the eight, US embassy spokeswoman Susan Stevenson said in a statement.

“We encourage the government of China to demonstrate respect for human rights, including freedom of expression and freedom of religion, of all people during the Olympic Games and beyond,” Stevenson said.

"These rights are protected by China's own constitution and by international human rights standards to which China has agreed," she added.

“We are disappointed that China has not used the occasion of the Olympics to demonstrate greater tolerance and openness,” the statement said.

Consular officials on Friday met the eight detained Americans, who did not claim any maltreatment, it said.

The 10-day sentence was given to the eight Americans, one British and one German citizen, in the harshest treatment so far of Tibet activists following a series of demonstrations in Beijing during the Olympics.

The police faxed a statement on Friday saying six foreigners arrested on Tuesday for "disturbing public order" will be detained for 10 days.

At least six of the detained Americans are believed to be from the US-based Students for a Free Tibet.

Since Aug 6, the group has held eight pro-Tibet protests in Beijing to put the spotlight on China's suppression of Tibetans.

Kate Woznow, the group's campaign director, told DPA on Friday that the six detained had not actually protested, but had documented, including filmed, some of the protests.

Altogether around 50 Tibet supporters from the group protested or assisted protesters in Beijing in the past two weeks.

The demonstrators unfurled pro-Tibet banners and displayed Tibetan flags on Tiananmen Square, near Olympic venues such as the Bird's Nest, and some chained themselves to a gate of a Beijing ethnic minorities park to protest.

In every incident, Beijing police quickly responded, taking away the banners and flags and detaining the protesters, deporting most of them almost immediately.

The London-based Free Tibet Campaign issued a statement urging British Prime Minister Gordon Brown, who arrived in Beijing on Friday for the Olympic closing ceremony, to demand an investigation into reports of a military crackdown and shootings in the Tibetan Kandze prefecture of south-west China's Sichuan province.