HONG KONG (Reuters) - The democracy movement in Chinese-ruled Hong Kong is facing a dark era, student protest leader Joshua Wong said on Wednesday, a day before an appeal court decides whether to send him and two other activists to jail.

Hong Kong student leader Joshua Wong poses for a photo, a day before an appeal verdict on charges relating to 2014 pro-democracy "Umbrella Movement", also known as "Occupy Central" protests ,in Hong Kong, China August 15, 2017. REUTERS/Tyrone Siu

The former British colony, which last month celebrated 20 years under Communist Party rule, was gridlocked by nearly three months of street protests in 2014 that failed to convince Beijing to allow full democracy in densely populated city.

The protest cemented the then 17-year-old Wong’s role at the forefront of the democracy movement, which has been on a roller coaster over the past year. The ride peaked with young candidates being elected on to the local legislature, before crashing down with a series of government-initiated lawsuits that ended with several being stripped of their seats.

Wong, now 20, who was sentenced to 80 hours of community service for illegal assembly connected to the 2014 protests before prosecutors sought a jail term, said the legal challenges had hit morale hard.

“It is the darkest era of the Hong Kong democratic movement,” Wong said.

“Hong Kong is not Hong Kong anymore and now we’re suffering from a serious threat because I guess in the next few years there will be nearly a hundred youth activists who will be sent to prison.”

Hong Kong became a “special administrative region” of China in 1997, since when it has been governed under a “one country, two systems” formula that guarantees a range of freedoms not enjoyed on the Chinese mainland, including a direct vote for half of the 70-seat Legislative Council.

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But activists say those freedoms have come under serious threat.

In recent months, dozens of protesters, mostly young people, have been jailed for their roles in various protests, including a violent demonstration that the government called a riot in early 2016.

This week, 13 mostly young activists were jailed for storming the Legislative Council in a separate incident, again after prosecutors pushed for harsher sentences than those handed down by lower courts.

Many activists have condemned the Department of Justice for its pursuit of jail terms for activists who have only recently become adults.

Wong is due to be sentenced on Thursday alongside former student leader Alex Chow and Nathan Law, 24, the youngest ever democratically elected lawmaker. He was expelled from office last month after a court ruled his oath of office, taken nearly a year ago, was invalid because he added words and adopted a tone of voice that “disrespected” China as the sovereign power.

They face a maximum three years in jail.

“The outlandish application seeking jail time is not about public order but is instead a craven political move to keep the trio out of the Legislative Council, as well as deter future protests,” China director at Human Rights Watch, Sophie Richardson, said in a statement.

Wong, who said he wants to run for a seat in the Legislative Council and pursue a political career, could be banned from running for five years if he were to be jailed for more than three months.

The Department of Justice, in response to questions from Reuters, said in a statement the three were convicted because they had broken the law.

“As the relevant judicial proceedings have not been completed, it is not appropriate for us to make further specific comments on the Application (by the prosecution), save that there is absolutely no basis to imply any political motive on the part of the Department of Justice in this case,” it said.