Beijing backed regime added the leader's name of pro-democracy protests in the city last year to more than 50 politicians detained in a massive crackdown on Thursday.
Mr. Wong, who s serving a 13 and half-month prison sentence for organizing and participating in an unauthorized protest in 2019, was arrested on Thursday on a new charge of subversion, the first time he has been detained under the new national security law.
He was taken away to give a statement on the new charge, according to a post on his Facebook page. Mr. Wong’s lawyer was unable to meet with him, and that Wong had been transferred back to prison after giving the statement, which was not disclosed.
In the morning, more than 1,000 police officers detained 53 prominent figures on charges of "subversion", a new national security crime that carries up to life in prison.
American human rights lawyer John Clancey was among 53 people busted in Hong Kong on Wednesday for allegedly violating the new national security law.
Footage of Mr. Clancey following his arrest circulated on Twitter, showing him walking with a cane and telling the Hong Kong people, Continue to work for democracy and human rights in Hong Kong, before he was whisked away in a car by police.
Mr. Clancey was the treasurer of the political group Power for Democracy, which was involved in the unofficial primaries.
Later in the afternoon, an American who works at law firm Ho Tse Wai & Partners, was granted bail, his associate said. At least some of the others arrested in the morning crackdown were released on bail from various police stations where they had been held.
Western democracies' reaction
Western nations have emphasised that Beijing is using its crackdown to shred the freedoms that were promised under the "One Country, Two Systems" setup when the British colony was returned to China.
The United States will not stand idly by while the people of Hong Kong suffer under Communist oppression, US Secretary of State Mike Pompeo said in a late-night statement after a day of political violence in Washington.
The United States will consider sanctions and other restrictions on any and all individuals and entities involved in executing this assault on the Hong Kong people, he added.
British foreign minister Dominic Raab called the detentions "a grievous attack on Hong Kong's rights and freedoms" and said Beijing "deliberately misled the world about the true purpose" of the security law.
Canada, France and the European Union also issued statements condemning sliding freedoms in Hong Kong and called for the release of those detained.
Beijing in full control of Hong Kong
Analysts say it is a new watershed moment for the semi-autonomous city.
Very clearly and unequivocally it demonstrates the Chinese government's control over Hong Kong, Dylan Loh, an expert on China's politics at Singapore's Nanyang Technological University, he stated.
There should be no illusions anymore that the central government is firmly in control, he added.
On Sunday, the traditional protests against the regime of Alexander Lukashenko were held in a seven cities in Belarusia.
Mr Pompeo appealed to Asian leaders for more courage to demand from Communist China accountability for the spreading deadly Wuhan virus around the world, and to stand against the CCP territorial and economic demands in Indo-Pacific.