More than 100 British lawmakers have signed a letter to the Chinese ambassador condemning what they described as "a systematic and calculated program of ethnic cleansing against the Uighur people" in China’s far-western Xinjiang region.

"When the world is presented with such overwhelming evidence of gross human rights abuses, nobody can turn a blind eye," read the cross-party letter, which was signed by 130 lawmakers Wednesday.

"We as Parliamentarians in the United Kingdom write to express our absolute condemnation of this oppression and call for it to end immediately."

The letter referred to reports of forced population control and mass detention of Uighur Muslims in Xinjiang, as well as video apparently showing a large number of blindfolded and shaven men waiting to be loaded onto trains. The lawmakers said the video –which was recently shown to Chinese Ambassador Liu Xiaoming during a BBC interview – bore "chilling" similarities to footage of Nazi concentration camps.

The Xinjiang region is home to around 10 million Uighurs. The Turkic Muslim group, which makes up around 45% of Xinjiang's population, has long accused China's authorities of cultural, religious and economic discrimination. About 7% of the Muslim population in Xinjiang, has been incarcerated in an expanding network of "political reeducation" camps, according to U.S. officials and United Nations experts.

Chinese officials have repeatedly derided allegations of genocide, forced sterilization and the mass detention of nearly 1 million Uighurs in Xinjiang as lies fabricated by anti-China forces. They maintain that the Uighurs are treated equally and that the Chinese government always protects the legitimate rights of ethnic minorities.

Moreover, 321 civil society groups including Human Rights Watch, Amnesty International and the International Service for Human Rights urged the United Nations to set up an international watchdog to address human rights violations by the Chinese government.

In an open letter published Wednesday, the groups said they are seeking greater scrutiny of and response to violations in places like Hong Kong, Tibet and Xinjiang, as well as beyond – such as through censorship, a development that hurts the environment and the targeting of rights defenders.

"The international community can no longer sit back and allow the Chinese authorities to trample on human rights at home and abroad," Joshua Rosenzweig of Amnesty International, one of the signatories, said in a joint statement.

The call for the creation of an "independent international mechanism" to focus on China's rights violations adds to recent international pressure on Beijing over its handling of issues like protests in Hong Kong and detention centers – what the government calls vocational or training centers – for Uighur Muslims and others in western Xinjiang region.

"China has systematically persecuted rights defenders in reprisal for their cooperation with U.N. human rights operations – torture, enforced disappearance, imprisonment, and stripping licenses from lawyers," said Renee Xia, director of Chinese Human Rights Defenders, in a statement. "The U.N. system should no longer tolerate such treatment."

The move follows a call by independent experts who work with the United Nations for a special session of the Human Rights Council focusing on the array of issues around China's rights record. Advocates insist that no country – no matter how large or powerful – should escape extra scrutiny of their rights records when warranted.

The groups also want U.N. Secretary-General Antonio Guterres and the U.N. High Commissioner for Human Rights, Michelle Bachelet, to "take responsibility for publicly addressing China’s sweeping rights violations," Human Rights Watch said in a statement.

The appeal comes ahead of the start of the 47-member-state Human Rights Council's fall session Monday. In its summer session, the council held an urgent debate on a rise in police violence against black people and repression of protests in the United States