Prime Minister Hun Sen yesterday wrote to UN Secretary-General Ban Ki-moon requesting access to the original, constitutionally mandated maps of Cambodia, saying he wanted to end the “extreme nationalism” whipped up by the opposition over the Vietnam border.

The request came as a Cambodia National Rescue Party lawmaker announced plans for a 10,000-strong march on a disputed patch of border in Svay Rieng, the scene of a violent clash between a CNRP-led group and Vietnamese authorities on June 28.

In the letter, dated yesterday, Hun Sen asks to borrow the original Bonne maps, scale 1/100,000, which were developed between 1933 and 1955 by French colonial authorities and deposited by late King Norodom Sihanouk with the UN in 1964.

Noting Sihanouk’s efforts to ensure the Kingdom’s borders were internationally respected, Hun Sun tells Ban Ki-moon the government needs the maps to “verify” its ongoing demarcation process.

The premier also said he sought the maps in a bid to “end the incitement of extreme nationalism” by “some quarters” in Cambodia, which “may lead to catastrophe”, a pointed reference to the CNRP’s recent push to highlight alleged encroachment by Vietnam.

He notes Cambodia’s “wellbeing”, “territorial integrity and sovereignty” and “the cause of peace and stability in the region”, among reasons for requesting cooperation.

The opposition has long accused the government of using maps developed with Vietnam during its occupation of the Kingdom in the 1980s to demarcate the border, which they say cedes Cambodian territory, instead of the French-developed ones cited in the constitution.

The CNRP has highlighted examples of alleged Vietnamese encroachment into Cambodia in Ratanakkiri, Kandal and Svay Rieng provinces, prompting official protests to Hanoi.

Last week, Va Kim Hong, the senior official in charge of border affairs, presented a number of maps used in the ongoing demarcation, stating that although developed in concert with Vietnam following a 2005 border treaty, the maps match those held by the UN.

Welcoming the prime minister’s request, CNRP lawmaker Um Sam An, among those involved in the June brawl, said the government should verify its maps and the placement of border posts together with the opposition, civil society and experts.

“If [we] verify and see that the posts are planted inside Khmer land, [we] must review and re-plant [border posts],” Sam An said.

Sam An also revealed the opposition would invite Cambodian People’s Party lawmakers to join a group of 10,000 people visiting border markers 202 and 203 in Svay Rieng’s Kampong Ro district on July 19.

The site has been a source of tension. On Saturday, a local NGO leader was detained and allegedly beaten by Vietnamese authorities after leading a group of students there.

The same area was the location of the June brawl between an opposition-led group and Vietnamese authorities, prompting a fierce rebuke from Vietnam, which will form a joint committee with Cambodia to investigate the violence.

Sam An said he would forewarn provincial authorities of the July 19 trip.

But Council of Ministers spokesman Phay Siphan yesterday said the planned march had the potential to end in violence and the government will take steps to see that it doesn’t take place.

“The government would negotiate to avoid this march happening along the border; it is provocative and eventually there will be violence,” he said.

Asked about the march yesterday, CNRP president Sam Rainsy was more equivocal than his lieutenant, saying that he had told Sam An to “calm down”, saying the party would “wait and see” the outcome of Hun Sen’s request.

However, he didn’t rule out a mass rally “if it’s the will of the people”.