The open letter comes as scores of human rights groups ask the International Olympic Committee to strip Beijing of the 2022 winter games.
Hundreds of organisations have urged the United Nations to probe rights violations in China as other groups called for Olympic chiefs to strip Beijing of the 2022 winter games.
In an open letter to UN Secretary-General Antonio Guterres, UN rights chief Michelle Bachelet as well as to member states on Wednesday, the 321 civil society groups called for international scrutiny of "the Chinese government's human rights violations."
"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.
In their letter, the NGOs pointed to an unprecedented call in June from dozens of independent UN experts for urgent action from the UN Human Rights Council to address the repression of fundamental freedoms in China.
The June statement had highlighted rights violations in Hong Kong, Tibet and against the majority-Muslim Uighurs in Xinjiang, as well as suppression of vital information in the context of the Covid-19 pandemic, and attacks on rights defenders, journalists, lawyers and government critics across the country.
On Wednesday, the NGOs stressed that they were also deeply concerned by "the impact of China's rights violations world-wide," pointing among other things to the targeting of rights defenders and internet censorship and digital surveillance.
Academic freedom under threat
They also pointed to allegations China was suppressing academic freedom in countries worldwide, and decried "the racist treatment of people in China, or by Chinese state actors in other parts of the world."
And they charged that Beijing was working to "distort the mandate of the UN Human Rights Council ... (by) opposing initiatives to bring scrutiny of serious rights violations and international crimes in countries around the world."
"A state that tries to hold itself above any kind of scrutiny presents a fundamental threat to human rights," the letter warned.
'Groundless and not worth refuting'
Sarah Brooks of the International Service for Human Rights, which also signed Wednesday's letter, meanwhile stressed in the joint statement "China's disdain for human rights no longer affects only its citizens."
"Its support for dictators and efforts to rewrite international standards are making the work of defending human rights harder than ever."
When asked about the letter, Chinese Foreign Ministry spokesperson Zhao Lijian said the "claims made by these organisations are groundless and not worth refuting." He dismissed it as an attempt to "politicise sports" that went against the Olympic spirit.
Wednesday's letter called on the Human Rights Council to host a special session to evaluate China's rights violations, and urged it to establish an "impartial and independent UN mechanism to closely monitor, analyse and report annually on the topic."
Rights groups ask IOC to move Olympics from China
More than 160 rights groups warned in a letter dated on Tuesday to International Olympic Committee President Thomas Bach that allowing the 2022 Games to go ahead could cause more repression in China.
The letter said that the 2008 Olympics had failed to improve China's human rights record and that since then, it has built “an Orwellian surveillance network” in Tibet and incarcerated more than a million Uighurs.