A Chinese court on Wednesday jailed 10 Hong Kong democracy activists for up to three years over a bid to flee the city by speedboat to Taiwan, as a crackdown on dissent in the territory intensifies.

The group were arrested by the Chinese coastguard on August 23 en route to the self-ruled island, which has opened its doors to Hongkongers seeking sanctuary.

The court in the southern city of Shenzhen sentenced Tang Kai-yin to three years in jail and Quinn Moon to two years for organising an illegal border crossing.

The eight others were sentenced to seven months behind bars for illegally crossing the border.

The sentencing follows the imposition of a sweeping new security law in Hong Kong this year that has given the government broad powers to prosecute political dissidents.

A number of activists have fled the city for overseas and political organisations have shuttered their doors as Beijing seeks to keep a lid on unrest that rocked the financial hub for months last year.

Officials earlier said that two minors from the so-called “Hong Kong 12”, aged 17 and 18, would be returned to Hong Kong after they admitted wrongdoing.

The pair arrived back in the city around noon on Wednesday.

The 10 adults in the group first appeared before the Shenzhen court on Monday, but the trial — like many in China’s opaque legal system — was not open to foreign reporters or diplomats.

These 10 were also fined up to 20,000 yuan (US$3,060) in addition to their jail terms.

But the Yantian District People’s Procuratorate said it would not pursue its case against the two teenagers, surnamed Hoang and Liu.

“Fleeing tyranny”

Families of the accused were only notified of the trial date three days before the hearing and were unable to attend due to the short notice and Covid-19 restrictions.

Their lawyers were barred from meeting the detainees, with authorities instead appointing state-approved legal representation.

The lawyers on Wednesday said the sentences were too heavy and the allegation of organising a border crossing was not substantiated.

The United States on Monday called for the immediate release of the group who it said was “fleeing tyranny”.

“Communist China will stop at nothing to prevent its people from seeking freedom elsewhere,” a US embassy spokesperson told AFP.

Some of the group were already facing prosecution in Hong Kong. The two minors face charges of conspiracy to commit arson and possession of an offensive weapon.

Amnesty International said in a statement that the group were at risk of torture serving sentences in mainland Chinese jails.

“These sentences meted out after an unfair trial lay bare the dangers faced by anybody who finds themselves tried under the Chinese criminal system,” said Amnesty International’s Asia-Pacific Regional Director Yamini Mishra.

“The Chinese authorities have shown the world once again that political activists will not receive a fair trial.”

China’s foreign ministry on Monday pushed back against comments by foreign countries on the case.

Washington must “immediately stop interfering in China’s internal affairs through the Hong Kong issue and immediately stop interfering in China’s judicial sovereignty”, spokesman Zhao Lijian told reporters.

“De facto secret”

In a joint letter over the weekend, the families said they “strongly condemn” the authorities’ decision to hold the trial in “de facto secret”.

The security law that now blankets Hong Kong gives authorities sweeping powers of prosecution for acts deemed terrorism, secession, subversion or collusion with foreign entities.

The city had enjoyed unique freedoms since its handover from former colonial power Britain in 1997, with a deal promising a “one country, two systems” arrangement for 50 years.

Beijing says the new security law was needed to restore peace and stability but critics have condemned it as a fatal attack on Hong Kong’s freedoms.