Three Hong Kong activists and the pro-democracy group behind the Umbrella Movement have been nominated for the 2018 Nobel Peace Prize for their role in pushing for reform in the Chinese territory.

Joshua Wong, Nathan Law and Alex Chow, as well as the "Umbrella Movement", were nominated by a group of US Congress members for the prestigious prize, a move Beijing denounced on Friday as a form of "meddling" in its internal affairs.

"This nomination could not be more timely as Hong Kong's long-cherished autonomy continues to erode, and Umbrella Movement leaders face reprisals simply for espousing basic human rights and freedoms," Marco Rubio, US senator and former Republican presidential candidate, said in a statement announcing the nomination.

Rubio said Wong and his fellow activists "are an inspiration" and their cause "has reverberations far beyond their city."

Chris Smith, a member of Congress who also signed the nomination, said the prize would be a fitting tribute to Chinese Nobel Peace Prize winner Liu Xiaobo, who died in China in 2017.

The letter was addressed to Berit Reiss-Anderson, chairman of the Nobel Peace Prize committee.

In a statement posted on social media on Friday, Wong said the nomination "would show the international community and [China's] President Xi how the young generation will persist in fighting for democracy, even if we have to face imprisonment or a permanent ban from public office".

In mid-January, Wong, 21, was sentenced to jail for the second time for his role in the 2014 pro-democracy protests in Hong Kong. He is currently out on bail for a separate case.

Wong had previously been jailed for six months in August 2017.

Wong's fellow nominee, Law, told Al Jazeera on Friday that they "are honoured to have taken part in ... the Umbrella Movement. Its spirit will continue to guide us and future generations".

'Domestic affairs'

In Beijing, the reaction was swift.

"Hong Kong's affairs are China's domestic affairs, and China firmly objects to anyone intervening through any means," China's foreign ministry said in a statement.

"We urge the relevant congressmen to stop meddling with Hong Kong's affairs," it said, urging the American politicians to "do more things that are conducive to the development of China-US ties, and not the opposite."

Starry Lee Wai-king, a pro-China Hong Kong politician, was quoted by the South China Morning Post calling the nomination "incomprehensible", adding that the 2014 protests were "not peaceful".

Hong Kong, a former British colony, was returned to China in 1997 under a "one country, two systems" agreement that ensured its freedoms, including a separate legal system.

But Beijing has ultimate control over the territory, and pro-democracy protesters in Hong Kong contest it is increasingly clamping down on the city's constitutionally enshrined freedoms.

In 2014, Hong Kong's pro-democracy activists staged massive protests that drew hundreds of thousands of protesters at its peak. The protesters were demanding an end to China's pre-screening of candidates for election of the autonomous region's leader.

The protest was later referred to as the Umbrella Movement, after the use of umbrellas as a tool for peaceful resistance against the Hong Kong police during the protests.

The demonstrations, which continued for almost three months, brought parts of Hong Kong to a standstill and sent alarms in mainland China.