HONG KONG — Jimmy Lai, the 73-year-old Hong Kong media tycoon and advocate for democracy, was denied bail Saturday after being charged the previous day under the semi-autonomous Chinese territory’s new national security law.

Lai faces a charge of collusion with foreign elements to endanger national security, apparently for tweets he made and interviews or commentaries he did with foreign media.

The Apple Daily, a feisty pro-democracy tabloid owned by Lai, said he is accused of asking a foreign country, organization or individual to impose sanctions or engage in other hostile activities against Hong Kong or China.

His case was adjourned to April 16 at the request of prosecutors, who said police needed time to review more than 1,000 tweets and comments made on his Twitter account, the Apple Daily reported.

The newspaper said his charge sheet listed several foreign politicians who followed Lai on Twitter and cited commentaries he wrote and interviews he did with foreign media.

Lai, who was already being held on other fraud charges after police raided his media company, could be seen handcuffed to a chain around his waist as guards led him to a van to go from prison to court. He wore a navy blazer and an open-neck shirt.

Beijing imposed the national security law on Hong Kong earlier this year after stormy protests in 2019 that started over an extradition bill and expanded to include demands for greater democracy in the former British colony.

The new law outlaws secession, subversion, terrorism and collusion with foreign forces to intervene in Hong Kong’s affairs. It has constricted free speech in the city, and democracy activists see it as a way to suppress dissent.

U.S. Secretary of State Mike Pompeo tweeted Saturday morning Asia time that the security law “makes a mockery of justice.” He called for Lai’s release, saying his only crime is speaking the truth about China’s authoritarian Communist Party government.

Lai, the highest-profile person charged under the security law, has also been arrested for other alleged offenses this year. He has been charged with taking part in unauthorized protests and with fraud over alleged violations of office lease terms.

He has advocated for other countries to take a harsher stance on China, and met with Pompeo and Vice President Mike Pence in the U.S. last year to discuss the extradition bill, which the Hong Kong government eventually withdrew.

Pence also tweeted about Lai, saying the charges against him are “an affront to freedom loving people around everywhere.”