HONG KONG (AP) — Three prominent Hong Kong pro-democracy activists were sentenced to prison Wednesday for a protest outside police headquarters as authorities stepped up a crackdown on opposition to tighten control by Beijing over the territory.

The activists — Joshua Wong, Agnes Chow and Ivan Lam — are among more than 10,000 people who have been arrested since June 2019 on charges related to protests against a proposed extradition law that expanded to include demands for greater democracy.

Beijing responded to the protests by imposing a sweeping national security law to crack down on dissent, which prompted more public opposition.

Wong, 24, is known abroad for his role as a student leader of the 2014 “Umbrella Revolution” protests in Hong Kong. He was sentenced to 13 1/2 months in prison after pleading guilty to organizing and taking part in the June 21, 2019, demonstration outside Hong Kong's police headquarters over the extradition bill and police use of force against protesters.

Chow was sentenced to 10 months by the West Kowloon Magistrates' Courts after pleading guilty to participating and inciting other protesters. Lam pleaded guilty to incitement and was sentenced to 7 months.

The crackdown has prompted accusations Beijing is violating the autonomy it promised when the former British colony was returned to China in 1997. It also has triggered warnings the ruling Communist Party is damaging Hong Kong’s appeal as a global business center and one of Asia’s most dynamic cities.

Other democracy advocates including media tycoon Jimmy Lai have also been arrested under the security law.

Hong Kong’s last British governor, Chris Patten criticized the sentencing, saying in a statement that it “is another grim example of China’s determination to put Hong Kong in handcuffs.”

Maria Adebahr, a spokeswoman for Germany’s foreign ministry, told reporters in Berlin that the sentences are “another building block in a series of worrisome developments that we have seen in connection with human and civil rights in Hong Kong during the last year."

Amnesty International said the three “must be released immediately and unconditionally.”

"Once again, the government has used the politically motivated charge of ‘inciting others to protest’ to prosecute people who have merely spoken out and protested peacefully,” said the group's Asia-Pacific regional director, Yamini Mishra.

“By targeting well-known activists from Hong Kong’s largely leaderless protest movement, authorities are sending a warning to anyone who dares openly criticize the government that they could be next.”

In Denmark, a Hong Kong pro-democracy activist and former lawmaker, Ted Hui, urged European nations on Wednesday to allow protesters in Hong Kong “a safe haven from the terror” of China’s Communist Party.

“The situation in Hong Kong is getting worse by the day and it is important that the world knows that Hong Kong is no longer a free city,” Hui said in an email to The Associated Press.

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Associated Press writers Kirsten Grieshaber in Berlin and Jan M. Olsen in Copenhagen, Denmark, contributed to this report.