PHNOM PENH (Reuters) - A Cambodian opposition member of parliament has been arrested for posting a map on Facebook professing to show that the government had ceded territory to Vietnam to whip up opposition, a government spokesman said on Monday.
Cambodia has for centuries fretted about its much bigger neighbours - Vietnam to the east and Thailand to the northwest - encroaching on its territory. The issue remains emotive and many Cambodians are suspicious of both countries.
Um Sam An, a member of the opposition Cambodia National Rescue Party (CNRP), was arrested on Sunday in the province of Siem Reap after arriving from overseas, a party colleague and fellow lawmaker said.
"He created a fake border map and used it as an incitement to overthrow the government," said government spokesman Phay Siphan.
Formal charges would be filed when he appeared before a court. Phay Siphan said he would be charged with forgery and incitement.
The opposition in Cambodia has for years accused Prime Minister Hun Sen of ceding land to Vietnam in the hope of turning voters against him.
The prime minister, who rose to power in the 1980s as part of a government that was backed by Vietnam, has dismissed the accusations.
The government spokesman said Um Sam An had repeatedly posted "fake" border maps on Facebook, accusing the government of ceding land.
Tension has been rising in Cambodia as Hun Sen's ruling party and the main opposition CNRP look to a 2018 general election that could be the biggest test of the prime minister's three-decade rule.
The CNRP condemned Um Sam An's arrest in statement on Monday.
An arrest warrant has been issued for CNRP leader Sam Rainsy on charges of defamation in several different cases.
He lives in self-imposed exile.
Another CNRP lawmaker, Hong Sok Hour, is in prison awaiting trial on an accusation that he posted on Facebook a fake government pledge to dissolve Cambodia's border with Vietnam.
(Reporting by Prak Chan Thul; Editing by Amy Sawitta Lefevre and Robert Birsel)