Human rights groups are calling on Thai authorities to drop charges against four activists who expressed dissent against the country's military rulers and are now being tried in a military court.

Human Rights Watch said Tuesday that the junta should stop prosecuting peaceful critics in the military courts, which are controlled by the junta.

The military, which took over power from a civilian government last May, issued a ban on political gatherings of five people or more. It also ordered security-related offenses to be handled by the military tribunals.

The four men were arrested last month for holding a campaign to call for martial law to be revoked.

An Amnesty International research director said the men would not face a fair trial and should be allowed to protest peacefully.