Hong Kong tycoon and pro-democracy advocate Jimmy Lai pleaded not guilty on Tuesday in a landmark trial, where he is accused of endangering China’s national security, as prosecutors laid out details of what they said was collusion with foreign forces.

Lai, a leading critic of the Chinese Communist Party, faces two counts of conspiracy to collude with foreign forces — including calling for sanctions against Hong Kong and Chinese officials — under a China-imposed national security law.

“Not guilty,” Lai said three times as each charge was read, appearing calm as he sat in a glass dock surrounded by guards and a court filled with family, supporters and foreign diplomats.

Lai, 76, the founder of now-shuttered pro-democracy newspaper Apple Daily, is also charged with conspiracy to publish seditious publications.

Western democracies, including Britain, the EU and the US, are watching closely, with the trial a diplomatic flashpoint and a test for Hong Kong’s judicial independence.

After marathon legal proceedings stretching over three years since Lai was arrested, the prosecution outlined for the first time in court the main details of their case, including meetings with senior figures in the former administration of US President Donald Trump.