Awwal 18, 1432 H / April 22, 2011, SPA -- Thai and Cambodian soldiers fought with rocket-propelled grenades and guns on their disputed border on Friday in a clash that killed six soldiers in the first major flare-up since a shaky ceasefire in February, according to Reuters. Both countries evacuated thousands of 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. 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 three fatalities, with six soldiers wounded. Defence ministry spokesman, Lieutenant General Chhum Socheat said at a news conference that Thai artillery shells had hit four Cambodian villages and Cambodian troops responded with rocket-propelled grenades. Soon after the clashes subsided, Cambodian Foreign Minister Hor Namhong sent a letter to the United Nations Security Council in New York, accusing Thailand of launching a "blatant" and "large-scale attack". A witness in one Thai village said occasional gunshots and shelling could still be heard hours after the clash. The heaviest fighting that broke out around daybreak had stopped after three hours, Chhum Socheat added. As a precaution, Thailand's government evacuated about 7,500 villagers, while Cambodian authorities moved several thousand people out of the area. FRAGILE CEASEFIRE The fighting is the most severe since three Thais and eight Cambodians were killed and dozens of people wounded over Feb. 4-7 in the bloodiest fighting in nearly two decades. As part of a ceasefire deal, Thailand and Cambodia agreed on Feb. 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. Thai Foreign Minister Kasit Piromya on Friday reiterated that stance. " There's a mechanism in place, so there's no need to run crying to ASEAN or the international community," Kasit told a news conference in Bangkok. In his letter to the United Nations, his Cambodian counterpart, Hor Namhong, said Thailand's refusal to allow third party mediation was a "pretext for using its larger and materially more sophisticated armed forces against Cambodia". Singapore's Foreign Ministry said it was "deeply concerned" about the unrest and called for restraint and dialogue. Indonesia, the current chair of ASEAN, of which Thailand and Cambodia are members, 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 the Preah Vihear temple, said the fighting had not spread to the ancient clifftop Hindu temple. An international court awarded Preah Vihear 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 has been a source of tension for generations and the two countries have been locked in a standoff since July 2008, when Preah Vihear was granted UNESCO World Heritage status. Thailand opposed the listing 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 colour 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 rumour of an imminent military coup swirled in Thailand overnight. The army has dismissed the rumours as baseless.