On the first day of closing submissions, one of the national security judges, Andrew Chan, said a verdict would "tentatively" come in three to four months, with 10 days set aside for closing submissions.

This is the first official indication of a potential end point for the legal proceedings, which have already stretched over 100 days in court since the trial began on Feb. 6.

The legal saga began with police raids on more than 50 of the city's leading democrats in early 2021 under a sweeping China-imposed national security law. Some Western governments, including the United States, have criticised the law as a tool of repression.

Beijing says the national security law brought stability to the city after months long pro-democracy protests in 2019.

The court case could see many leading democrats jailed for life.

Throughout the trial, government prosecutors have accused the democrats of hatching a conspiracy to cause a constitutional crisis and to subvert the authorities by unlawful means.

The prosecutors alleged that after organising a primary election aimed at maximising the democratic opposition's chances of a majority in the legislature, the democrats would then seek to "indiscriminately veto" government budgets to push the government to respond to the demands of democratic protesters.

The aim was to subvert state power, or force Hong Kong's leader to resign, the prosecutors said.

During the closing submission, prosecutor Jonathan Man argued that it was quite clear that acts of subversion had taken place, even without actual violence.

"Nowadays physical violence would not be necessary," to carry out subversion, Man told the court, saying such acts were often carried out through digital means including social media.

"Communication with the public is much easier, (it's) easy to manipulate those means in order to endanger national security," he added.

Some defence lawyers argued, however, in their closing submissions that the right to veto a budget is allowed for under the city's mini constitution, the Basic Law.

Most of the democrats have been detained for more than 1,000 days since Feb. 28, 2021, on national security grounds, and were subjected to marathon bail hearings. The case has been repeatedly delayed as prosecutors requested more time to prepare. Only 13 of the original 47 democrats were granted bail.

Thirty-one of the 47 charged have pleaded guilty - which could qualify them for reduced sentences. Only 16 are not pleading guilty, including former journalist Gwyneth Ho; activists Owen Chow and Gordon Ng; and ex-democratic lawmakers Leung Kwok-hung, Lam Cheuk-ting and Helena Wong.

Those who have pleaded guilty include former law professor Benny Tai and activist Joshua Wong, who will be sentenced after the trial. Four who pleaded guilty have become prosecution witnesses.