A Cambodian court has rejected an opposition senator's request for bail and opened a trial against him on charges that carry penalties of up to 17 years in prison for comments he posted on Facebook.

Hong Sok Hour was brought to the Phnom Penh Municipal Court on Friday in an orange prison uniform.

He was arrested Aug. 15 arrest after Prime Minister Hun Sen said his comments amounted to treason.

In comments posted on Facebook, Hong Sok Hour criticized a 36-year-old border agreement with Vietnam.

He was charged with inciting chaos and two other charges, which he denies.

Human Rights Watch has called on authorities to drop the case, saying Hong Sok Hour has been wrongfully charged and that prosecuting him marks the government's latest crackdown on the political opposition.