Phnom Penh: Cambodian Prime Minister Hun Sen on Thursday ordered the arrest of an opposition senator for "treason" after accusing him of posting a fake document about the border with neighbouring Vietnam on social media.
The command to arrest Senator Hong Sok Hour, who belongs to the opposition Sam Rainsy Party (SRP), comes amid an uptick in the campaign by the kingdom`s main opposition Cambodia National Rescue Party (CNRP) to combat alleged encroachment by Vietnam.
The SRP is one of a handful of parties unrepresented in Cambodia`s lower house of parliament that has backed the CNRP in its protests against the way in which the 1,270-kilometre (787-mile) border with Vietnam, still not fully demarcated, has been negotiated.
Strongman Hun Sen said he asked police to arrest the senator after he posted a "fake" and "doctored" version of an old treaty about the border on his Facebook page.
"This is an act of treason which is unforgivable," said the prime minister, announcing the arrest order midway through a graduation ceremony speech in Phnom Penh.
He added that the senator, who carries both Cambodian and French citizenship, would be stripped of parliamentary immunity from prosecution and urged foreign embassies against providing asylum.
Cambodia`s opposition party has long been critical of Phnom Penh`s cosy ties with Hanoi and routinely accuses Vietnam of taking Cambodian territory and Hun Sen`s government of using fake maps to demarcate the border.
Hong Sok Hour, chairman of the Senate`s anti-corruption committee, has played a key role in the CNRP campaign in recent years.
On Thursday the SRP issued a statement denying the senator committed treason, saying he would issue a public correction if his comments were inaccurate.
It was not immediately possible to reach the senator for comment or verify the contents of any Facebook posting.
The increasingly vocal CNRP allegations have prompted the premier to ask France, the United States, Britain and the United Nations for any original maps of Cambodia in order to check against the maps being used by the government.
On Thursday Hun Sen said the UN would lend his government a set of digital maps next week.
Rhetorical and sometimes physical attacks by opposition lawmakers and activists on the Vietnamese border have become a common occurrence in recent years.
Last month Hanoi said some 250 Cambodian activists, including a CNRP lawmaker, attacked Vietnamese police and citizens after illegal entering the country, strongly condemning the move.
Vietnam`s troops invaded to oust Cambodia`s genocidal Khmer Rouge regime in 1979 and stayed in the country for a decade before withdrawing in 1989.
Ties between Hanoi and Phnom Penh have remained friendly under Hun Sen who rose to power during the Vietnamese occupation and has run Cambodia for the last 30 years.
The CNRP formed following a merger between members of the SRP -- named after the current CNRP leader Sam Rainsy -- and The Human Rights party, ahead of 2013 elections.
The three parties remain in alliance.