The campaigners reportedly represented Tibetan, Uyghur, Southern Mongolian, Hongkonger, Taiwanese, and Chinese people.

The group delivered the letter, which was reportedly signed by 200 rights groups, on June 23 to coincide with Olympic Day.

Campaigners said rights groups and activists in 60 cities marked #NoBeijing2022 Global Day of Action, which saw them call for world leaders, National Olympic Committees and Olympic sponsors to boycott the Games in Beijing.

China has been accused of crimes including using forced Uyghur labour, operating a mass surveillance programme, detaining thousands in internment camps, carrying out forced sterilisations and intentionally destroying Uyghur heritage.

Beijing claims the camps are training centres designed to stamp out Islamist extremism and separatism, and denies the charges laid against it.

The campaigners’ letter was addressed to NBCUniversal chief executive Jeff Shell and NBC Olympics President Gary Zenkel.

"By going ahead with the broadcast NBC will be legitimizing these abuses and promoting the ‘Genocide Games’," the letter reportedly read.

A statement from campaigners said they held banners saying "Boycott Beijing 2022 Genocide Games #NoRightsNoGames" and "NBC: Do The Right Thing - #BoycottBeijing2022", as well as signs with NBC’s official logo for the Beijing Olympics with the word ‘Genocide’ printed next to the logo.

Campaigners said they were denied entry to the building and asked to leave the premises.

A representative from NBC reportedly listened to a joint statement by the campaigners.

Campaigners have sought to target the broadcaster, following similar efforts with sponsors of the Games.

In April, more than 200 global campaign groups signed an open letter urging chocolate bar brand Snickers to "immediately cancel" its sponsorship of Beijing 2022 due to China's human rights situation.

Mandie McKeown, executive director of the International Tibet Network, signed the letter on behalf of the coalition of campaign groups and requested a meeting with Mars Wrigley representatives.

A similar campaign was launched against fellow sponsor Airbnb in January.

Tensions between the US and China are strained, with American authorities joining the European Union, Canada and the United Kingdom in imposing sanctions on China earlier this year in response to alleged abuses of human rights in Xinjiang.

China issued a series of sanctions in response.

The US Senate last week passed a Bill confirming plans for a diplomatic boycott of Beijing 2022.

The bipartisan Bill introduces a series of measures aimed at tackling Chinese foreign policy and economic influence.

The legislation would prevent the US Secretary of State Antony Blinken from providing any Federal funds to support or facilitate the attendance of any American Government employee at the Games.

The Bill still requires approval from the US House of Representatives, before it could be signed into law by US President Joe Biden.