Thai and Cambodian soldiers fought with rocket-propelled grenades and guns on their disputed border on Friday in a morning clash that killed three Thai soldiers and wounded 13 in the first major flare-up since a shaky ceasefire in February.
Both sides evacuated villagers and accused each other of firing first in the thick, disputed jungle around Ta Moan and Ta Krabei temples in the northeastern Thai province of Surin, about 150 km (93 miles) southwest of the 900-year-old Preah Vihear temple, which saw a deadly stand-off in February.
"Cambodia started attacking our temporary base with artillery fire and we responded to defend ourselves," said Lieutenant General Thawatchai Samutsakorn of the Thai army.
"Tensions have eased for now but both sides are holding position."
Three Thai paramilitary rangers were killed and 13 wounded, said Thai army spokeswoman Sirichan Ngathong, adding that fighting began after Cambodian troops altered a bunker in the area and moved closer in violation of a ceasefire pact.
"When warned, Cambodian troops stepped closer and started firing," she said.
Cambodia suffered fatalities but it was unclear how many, said Cambodia's defense ministry spokesman, Lieutenant General Chhum Socheat. He said troops responded to Thai fire with rocket-propelled grenades.
A witness in one Thai village said occasional gunshots and shelling could still be heard hours after the clash, although the heaviest fighting had stopped. The clash began around dawn and lasted about three hours, Chhum Socheat added.
As a precaution, the Thai government evacuated about 7,500 villagers from the area. Cambodian authorities evacuated about 200 families, according to local officials.
The fighting is the most severe since three Thais and eight Cambodians were killed and dozens of people wounded over February 4-7 in the bloodiest fighting in nearly two decades.
As part of a ceasefire deal, Thailand and Cambodia agreed on February 22 to allow unarmed military observers from Indonesia to be posted along their border.
But that arrangement -- brokered by a meeting of Association for South East Asian Nations (ASEAN) foreign ministers in Jakarta -- has yet to be put in place. Thailand said international observers were not required, insisting the two countries should resolve the issue bilaterally.
"There's a mechanism in place, so there's no need to run crying to ASEAN or the international community," Thai Foreign Minister Kasit Piromya told a news conference in Bangkok.
He was responding a letter from Cambodia addressed to ASEAN, stating that Thailand had staged "a large-scale attack" on its neighbor.
Singapore's Foreign Ministry said it was "deeply concerned" and called for restraint and dialogue. Indonesia, the current chair of ASEAN, urged both sides to stop fighting.
Indonesia "strongly calls for the immediate cessation of hostilities between Cambodia and Thailand; for the two sides to continue to resolve their differences through peaceful means," it said in a statement.
Chhay Mao, a major in the Cambodian army stationed at Preah Vihear temple, said the fighting had not spread to the ancient clifftop Hindu temple. "It is quiet at Preah Vihear now but we are ready on our side," he said.
An international court awarded the temple to Cambodia 49 years ago but both countries lay claim to a 4.6 sq km (1.8 sq mile) patch of land around it.
The temple, known as Preah Vihear in Cambodia and Khao Phra Viharn in Thailand, sits on land that forms a natural border and has been a source of tension for generations.
Thailand and Cambodia have been locked in a standoff since July 2008, when Preah Vihear was granted UNESCO World Heritage status, which Thailand opposed on grounds that the land around the temple had never been demarcated.
But the reasons behind this year's deadly skirmishes are murky and both sides typically blame each other.
Some analysts say some hawkish Thai generals and their ultra-nationalist allies, who wear the Thai king's color of yellow at protests, may be trying to create a pretext to stage a coup and cancel elections expected in June or July.
Others say it may be a breakdown in communication at a time of strained relations and unease after a rumor of an imminent military coup swirled in Thailand overnight. The army has dismissed the rumors as baseless.
Thailand and Cambodia are both members of the ASEAN regional grouping which plans to form a European-style single market by 2015.