PHNOM PENH - A Cambodian opposition senator could be jailed for 17 years after a court charged him Sunday over the posting of a disputed document on social media about the border with Vietnam.

Anti-Vietnamese sentiment is strong in parts of Cambodia and is often used by the opposition as a touchstone issue to rally support. Senator Hong Sok Hour was arrested Saturday days after Cambodian Prime Minister Hun Sen accused him of committing treason by posting a "doctored" version of an old treaty about the border on his Facebook page. The legal move follows an uptick in the campaign by the kingdom's main opposition Cambodia National Rescue Party (CNRP) to combat alleged encroachment by Vietnam. Hong Sok Hour belongs to a CNRP-affliated party active in the Cambodian Senate.

In a rare Sunday sitting a Phnom Penh court charged the senator with "falsifying public documents, using fake public documents, incitement causing unrest," according to a letter from the prosecution seen by AFP.

"He faces up to 10 years in jail for the first charge, up to five for the second and up to two for the third," defence lawyer Sam Sokong told AFP.

The neighbours have shared a testy relationship since Vietnam's troops invaded to oust Cambodia's genocidal Khmer Rouge regime in 1979 before withdrawing a decade later.

Strongman Prime Minister Hun Sen, who has ruled Cambodia for three decades, is highly sensitive to criticism that he is too soft on Vietnam over the disputed areas of the shared border.