Cambodia said on Sunday it had asked the International Court of Justice to resolve its border disputes with Thailand, after a flare-up in their long-running row led the Southeast Asian neighbours to mobilise troops on both sides of the border.

A Cambodian soldier was killed in a brief skirmish on May 28 in a confrontation over the 820-km (510-mile) frontier, parts of which are undemarcated and claimed by both nations.

“Cambodia chooses a peaceful resolution based on international law through the ICJ mechanism for solving the border dispute,” Prime Minister Hun Manet posted on his Facebook page.

The post showed a picture of Deputy Prime Minister Prak Sokhonn holding an envelope that Hun Manet said contained a formal letter to the ICJ in The Hague, often called the World Court.

The Thai Foreign Ministry did not immediately respond to a request for comment on Cambodia's move. Bangkok has previously said it has never recognised the court's jurisdiction and prefers to settle the disputes through bilateral mechanisms.

Talks on border demarcation over the weekend between officials from both countries were inconclusive with both sides pledging to de-escalate tensions and continue dialogue.

Cambodia said in a statement that it had proposed to Thailand the two countries should jointly bring the four dispute areas to the ICJ and that these areas should no longer be included in future bilateral talks on border demarcation.

Cambodia also said that it would begin legal proceedings at the ICJ independently, despite Thailand's rejection of the court's jurisdiction.

Thailand, on the other hand, made no mention of the four disputed areas or the ICJ, saying only that "both sides will continue discussions and joint implementation" of border demarcation talks. Thailand is set to host the next meeting in September.

Hun Manet said the disputes at the four border areas, including the one where the fatal clash took place, are "complicated and have high risks of armed clashes and where bilateral mechanisms cannot solve".

He did not disclose the contents of the letter, which were not visible in the picture.

Cambodia has twice successfully sought ICJ resolutions, in 1962 on the ownership of the disputed Preah Vihear temple and in 2013, after it sought clarification of jurisdiction of the land around the temple.

Although both governments have pledged to handle the issue through dialogue and to calm nationalist fervour, Bangkok has threatened to close the border and cut off electricity supplies to its neighbour.

Phnom Penh announced it would cease buying Thai electric power, internet bandwidth and produce. It has also ordered local television stations not to screen Thai films.