Hong Kong democracy activist Joshua Wong was sentenced to 10 more years in jail in the Chinese territory on Thursday for colluding with foreign powers.

Wong, who became internationally renowned during the "Umbrella Movement" that convulsed Hong Kong in 2014, has already spent almost six years behind bars and is now not due for release until late 2036.

The former student leader, who turned 30 last month, was previously expected to be freed in January after serving four years and eight months for "subversion" under a Beijing-imposed national security law.

But Hong Kong authorities used the same law to charge Wong again in June last year, accusing him of collusion with other countries and entities to impose sanctions against the finance hub and China.

Pro-democracy tycoon Jimmy Lai, founder of the now-defunct Apple Daily newspaper, was given 20 years in February under the same legislation.

The court on Thursday described Wong and fellow student leader Nathan Law -- in self-imposed exile and wanted by authorities -- as "two ring-leaders or masterminds" of a conspiracy to endanger national security.

Wong was potentially facing a life term as his offence was deemed to be "of a grave nature", judge William Tam said.

But he decided an "appropriate starting point" for Wong's offence was 13 years, reduced to 10 because of his guilty plea.

With a heavy police presence outside, Wong entered the dock looking calm in a blue shirt and black glasses, nodding to supporters.

Wong said in his mitigation letter to court, seen by AFP, that he had hoped to leave prison in 2027, but the new charge made him felt he was back at the beginning.

He added that his future would not be defined by things that happened to him before 2020, and that the years he has spent behind bars have been the "most profound lessons" of his life.

After the sentencing, Wong thanked and waved to his supporters as he left. Some wept and were heard saying: "We'll be waiting for your release."

Wong's fate shows that Beijing "is keeping a tight rein over Hong Kong and there's no scope for turning back to the more relaxed days before 2019", Steve Tsang, director of the China Institute at SOAS Univesity of London, told AFP before the sentencing.

Human Rights Watch said his sentence "cruel and unjust", and urged foreign governments to "impose targeted sanctions on officials responsible for Hong Kong's growing repression".

Steve Li, chief superintendent of the police's National Security Department, welcomed the sentencing, which he said "evidently proved" Wong's efforts to rouse foreign sanctions were "futile".

Political star

Wong rose to prominence during Hong Kong's 2014 protests, known as the Umbrella Movement, and has been in and out of jail since 2017.

Authorities said Wong started international lobbying as early as 2016, when he promoted a bill -- the Hong Kong Human Rights and Democracy Act -- that would allow the US president to impose sanctions in response to rights violations in the city.

Durring Hong Kong's massive pro-democracy protests in 2019, Wong was part of a delegation to the United States to lobby for the bill, which eventually passed.

The following year, Beijing imposed the sweeping national security law on Hong Kong that effectively quashed dissent, prompting opposition groups to disband and activists to flee the city.

At the time, Wong vowed to "continue to defend my home -- Hong Kong -- until they silence me".

He was among dozens of pro-democracy figures jailed for "subversion" in 2024, in what was Hong Kong's largest national security trial. Some of them have since been released.

'Worried'

Louis Lee, a friend of the activist, said before the sentencing that Wong remained "energetic" in prison, but was sometimes "worried and nervous".

During prison visits, the former student leader looked disappointed and would sigh from time to time, Lee recalled.

Margaret Chan, a 61-year-old retiree and a long-time supporter of Wong, told AFP that she was "too heartbroken" as the judge handed down the sentencing.

"He will be in his middle age by the time he is released," she said.