PHUM SARON, Thailand (Reuters) - Thai and Cambodian troops clashed for a fourth straight day on Monday over a disputed border area surrounding a 900-year-old mountaintop temple, deepening political uncertainty in Bangkok and prompting Cambodia to urge U.N. intervention.
Several hours of shelling and machine gun fire subsided at around 11 a.m. (0400 GMT), creating an uneasy peace in the 4.6-sq-km (two-sq-mile) contested area around the Preah Vihear temple claimed by both Southeast Asian neighbours.
Cambodia's government said Monday's fighting had killed five people and wounded 45 others on its side of the border. It did not say whether the casualties were troops or civilians.
Both sides blame the other for clashes that have killed at least two Thais and eight Cambodians since Friday and unleashed nationalist passions in Bangkok, energizing "yellowshirt" protesters demanding that Thailand's government step down.
Reasons behind the fighting remain murky. Some analysts reckon hawkish Thai generals and nationalist allies may be trying to topple Thailand's government or even create a pretext to stage another coup and cancel elections expected this year.
Others say it may be a simple breakdown in communication channels at a time of strained relations over Cambodia's flying of a national flag in the disputed area and laying of a stone tablet inscribed with "This is Cambodia."
The clashes pushed down shares in Thai firms with businesses in Cambodia, led by a 1.8 percent loss in satellite firm Thaicom, with its telecom service in Cambodia contributing 10 percent of revenue.
In Phum Saron, an evacuated village in Thailand's Si Sa Ket province where Cambodian artillery struck several homes and a school on Sunday, Thai soldiers guarded buildings and said it was unclear if more fighting loomed.
On the Cambodian side of the frontier, pigs and chickens roamed deserted villages. Schools and temples were turned into makeshift refugee centres. Naked children played as people collected firewood or queued for handouts of rice and water.
Several trucks each carrying at least 100 Cambodian infantry soldiers were seen racing toward the conflict zone.
Cambodian Prime Minister Hun Sen called on the U.N. Security Council to convene an urgent meeting, accusing Thailand of "repeated acts of aggression" that have killed Cambodians and caused a wing of the temple to collapse.
Thai Prime Minister Abhisit Vejjajiva wrote to the Security Council, saying Cambodia was trying to internationalize a bilateral issue and accusing its troops of launching attacks that were "pre-meditated and well-planned in advance." He said the Thai troops had no choice but to engage in self defence.
In New York, the Security Council on Monday, discussed letters from both countries after a meeting on unrelated issues but indicated it would wait to see what came of mediation efforts by the Association of Southeast Asian Nations (ASEAN).
This month's council president, Brazilian Ambassador Maria Luiza Ribeiro Viotti, told reporters the 15 council members "took cognizance" of the letters but did not schedule a formal meeting on the dispute.
"They expressed their willingness to hold a Security Council meeting pending an assessment of the ongoing regional mediation efforts," she said, adding that council members called for a ceasefire and peaceful resolution of the dispute.
ASEAN dispatched Indonesian Foreign Minister Marty Natalegawa to Cambodia on Monday in a bid to defuse the crisis. He was scheduled to meet with Thai government officials in Bangkok on Tuesday. Viotti said the council expressed its support for Natalegawa's mediation work.
Natalegawa called for dialogue and for both sides to honour a cease-fire agreed on Friday to protect ASEAN's integrity ahead of the formation of its European Union-style community.
"On the eve of an ASEAN community in 2015, guns must be silent in Southeast Asia," he told reporters in Phnom Penh.
The dispute threatens to worsen hostility between Thai political factions ahead of this year's expected election.
The "yellow shirts" group of protesters, whose crippling rallies helped bring Abhisit to power, have turned against him in recent weeks, calling for a tougher line against Cambodia.
In 2008, they occupied state offices for three months and blockaded Bangkok's main airport until a court expelled a government allied with former Prime Minister Thaksin Shinawatra, a step that led to Abhisit taking power.
Thailand's police chief said he would seek cabinet approval on Tuesday to impose the Internal Security Act so security forces could stop the protesters from occupying government buildings in Bangkok in demonstrations planned for Friday.
The temple, known as Preah Vihear, or "Mountain of the Sacred Temple," in Cambodia and Khao Phra Viharn in Thailand, sits on a triangular plateau that forms a natural border.
Both sides have been locked in a standoff since July 2008, when Preah Vihear was granted UNESCO World Heritage status, which Thailand opposed on grounds that territory around the temple had never been demarcated.
The International Court of Justice in 1962 awarded the temple to Cambodia, which uses a century-old French map as the basis for its territorial claims, but the ruling failed to determine ownership of the scrub next to it.
(Additional reporting by Prak Chan Thul and Jared Ferrie in Phnom Penh, Damir Sagolj in Anglong Veng and Pracha Hariraksapitak in Bangkok; Writing by Jason Szep; Editing by Philip Barbara)