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 UN 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. Cambodias government said Mondays 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 Thailands government step down. Reasons behind the fighting remain murky. Some analysts reckon hawkish Thai generals and nationalist allies may be trying to topple Thailands 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 Cambodias 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 Thailands 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. 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 towards the conflict zone. Cambodian Prime Minister Hun Sen called on the UN 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. In a speech in the Cambodian capital Phnom Penh, Hun Sen directly addressed his Thai counterpart. We will go to the UN Security Council whether you like it or not, he said during a university graduation ceremony, calling on the United Nations to deploy peacekeeping troops to the area. The armed clash is threatening regional security. 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-mediated and well-planned in advance. Thai troops had no choice but to exercise the inherent right of self defence, Abhisit said. In New York, diplomats said the Security Council had received letters from both countries, and this months council president, Brazilian Ambassador Maria Luiza Ribeiro Viotti, had met Thai and Cambodian diplomats on Sunday. The issue would be raised under any other business after a council meeting on Monday on the UN peacekeeping mission in Congo, they said. One diplomat said that if Thai-Cambodian talks failed, I think our preference would be that ASEAN (the Association of South East Asian Nations) should have the first try at mediating 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. Natalegawa called for dialogue and for both sides to honour a cease-fire agreed on Friday to protect ASEANs 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 years 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 him to take a tougher line against Cambodia. In 2008, they occupied state offices for three months and blockaded Bangkoks main airport until a court expelled a government allied with former Prime Minister Thaksin Shinawatra, a step that led to Abhisit taking power. Thailands 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.