With its friezes of kings, gods and elephants, its ancient buildings and its location at the top of a beetling cliff, the temple of Preah Vihear is one of the most spectacular and historic sites in South-East Asia. Now it is threatening to make history for a different reason, as the first World Heritage Site to become a battleground.

Thai and Cambodian troops pulled guns on one another in a tense stand-off in the 1,100-year-old Hindu temple, after several days of increasing military tension. Stoked by a build-up of soldiers, accusations of corruption and a developing political crisis in Thailand, Preah Vihear has emerged as Asia’s newest flashpoint.

About 400 Thai and 200 Cambodian troops have moved into the temple area since Tuesday, after three Thai activists were detained briefly for entering the temple to assert Bangkok’s claim to the land. Yesterday a Cambodian general reported that soldiers from both sides levelled weapons at one another on Thursday night, after the Thais drove Cambodian forces out of one of the temple buildings. “We exercised patience to prevent weapons from being fired,” Brigadier-General Chea Keo said. He said that the Cambodian troops had been escorting monks and nuns, but withdrew after the encounter.

Perched on the top of a 1,600ft (488m) cliff, Preah Vihear is far more accessible from Thailand than from Cambodia. The territory was awarded to Cambodia in a ruling by the International Court of Justice in 1962, after legal arguments about the validity of maps produced during Cambodia’s French colonial period. Its inaccessible position made it a natural fortress — it was the last hold-out of the forces of the Lon Nol regime, driven out by the genocidal Khmer Rouge in 1975.

Even after their own defeat, Khmer Rouge forces held out in the temple until 1998.

Ill-feeling was defused because Thai locals and tourists were allowed to visit the temple freely from Thailand without a visa, and the dispute was largely forgotten until this month when the UN cultural organisation, Unesco, granted an application for Preah Vihear to receive World Heritage status. The decision would do much to promote tourism to Preah Vihear and bring business to both sides. When it turned out that the Thai Government had supported the application, there was an uproar in Bangkok.

Since its election victory last December, the Government of the Prime Minister, Samak Sundaravej, has been under increasing pressure from protesters who accuse it of being the puppet of the country’s deposed leader, Thaksin Shinawatra. The Preah Vihear debacle has enabled them to portray Mr Samak and his ministers as self-seeking cynics who have sold out Thai territory, allegedly in return for concessions for the tourist industry.

Thailand’s constitutional court ruled earlier this month that endorsing the Unesco application was illegal; Mr Samak’s foreign minister resigned as a result. It is unclear why Thai troops have entered the temple area. They may have gone at the behest of a government anxious to demonstrate its nationalist potential. Or they may have been sent at the initiative of military officers, as a warning to Mr Samak whose friend, Mr Thaksin, was himself ousted in a military coup.

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