He also asked for the immediate release of 12 Hong Kong pro-democracy activists who were detained in China for fleeing to Taiwan in order to escape Beijing's exercise of the draconian National Security Law.

He tweeted: "The Hong Kong 12 should be released immediately. Their so-called “crime” was to flee tyranny. Communist China today is turning Hong Kong into the East Berlin of yesteryear, actively preventing its own people from seeking freedom elsewhere."

Chinese prosecutors have officially indicted 10 of the 12 Hong Kongers detained in mainland China, months after they were arrested for attempting to flee to Taiwan by boat, reports CNN.

The 12 activists -- most of whom were on bail or facing charges in Hong Kong related to last year's anti-government protests -- boarded a speedboat in the tiny fishing village of Po Toi O on August 23, hoping to follow others who had fled to the self-governing island of Taiwan, about 700 kilometers (440 miles) away, the news channel reported.

They were stopped by coast guard vessels.

They have been detained in mainland China ever since while their families have desperately lobbied for their return, saying the 12 have been denied access to lawyers and abused while in Chinese custody, reports CNN.