BANGKOK: Cambodia withdrew on Wednesday from the Southeast Asian Games, an Olympic official said, as a border conflict with hosts Thailand escalated and forced a mass exodus of civilians from both sides of the disputed frontier.

At least 11 soldiers and civilians have been killed on both sides, according to officials, as renewed hostilities derailed a US-brokered truce.

Cambodia had already pulled out of eight sports at the Thailand-hosted Games, but National Olympic Committee of Cambodia (NOCC) chief Vath Chamroeun wrote in a letter Wednesday to the Southeast Asian Games Federation that it would bring all of the country’s athletes home.

“Due to serious concerns and requests from the families of our athletes to have their relatives return home immediately, NOCC must withdraw all of our delegation and arrange for their prompt return to Cambodia for safety reasons,” he wrote.

The Games officially opened on Tuesday and run until Dec. 20 in Bangkok and the nearby coastal province of Chonburi, with thousands of athletes from southeast Asian countries competing in events ranging from football and fencing to skateboarding, sailing and combat sports.

But renewed fighting this week between Thailand and Cambodia over a long-standing border dispute has overshadowed the Games.

There was tightened security at Tuesday’s opening ceremony at the Rajamangala National Stadium in Bangkok attended by Thai royals and featuring Thai K-pop idol BamBam.

A small delegation from Cambodia took part in the athletes’ parade.

This week’s clashes are the deadliest since five days of fighting in July that killed dozens before a shaky truce was agreed, in large part owing to intervention by US President Donald Trump.

Both sides blame each other for sparking the renewed clashes, which on Tuesday expanded to five provinces of both Thailand and Cambodia, according to an AFP tally of official accounts.

More than 500,000 people have fled their homes to safety in Thailand and Cambodia since the conflict reignited, both governments said on Wednesday, surpassing the total number evacuated during similar clashes earlier this year.

The dispute centers on a century-old disagreement over borders mapped during France’s colonial rule in the region, with both sides claiming a smattering of boundary temples.