PHNOM PENH, Cambodia — Machine-gun and artillery fire echoed across the frontier between Thailand and Cambodia on Monday as fighting between their troops erupted for a fourth day near an 11th century temple that has been caught in the crossfire.

Cambodian government spokesman Phay Siphan said clashes began again early Monday after halting around midnight. There was no immediate comment from Thai authorities, but an Associated Press reporter in the area said the sound of gunfire and artillery could be heard.

The fighting began Friday, and Cambodian officials say Thai artillery on Sunday collapsed part of a wall of the Preah Vihear temple, a U.N. World Heritage Site. Thai officials have dismissed the reports as propaganda, and the extent of the damage is unknown. The temple, built more than 900 years ago, belongs to Cambodia under a 1962 World Court ruling disputed by many Thais.

Cambodian Prime Minister Hun Sen has warned that the fighting poses a threat to regional stability. He said the latest clash was sparked after Thai soldiers crossed the border in search of a slain comrade, and Cambodians opened fire to repel them. He spoke Monday during a university graduation ceremony in the capital, Phnom Penh.

On Sunday night, a Thai army spokesman said about 10 Thai soldiers were wounded. Hun Sen said then that the clashes Sunday resulted in "more human casualties and damages" but did not elaborate.

Hun Sen has sent a letter to the U.N. Security Council calling for an emergency meeting to help end the fighting.

At least five people have died in the border clashes — some of the fiercest in years.

The crumbling stone temple, which sits several hundred feet from Thailand’s eastern border with Cambodia, has fueled nationalist sentiment on both sides of the disputed frontier for decades.

In 1962, the World Court determined that the temple belongs to Cambodia. Thai nationalists dispute the ruling and have seized on it as a domestic political issue, and the conflict has sparked sporadic, brief battles between the two neighbors over the last few years.

On Sunday, the Cambodian government issued a statement saying "a wing of our Preah Vihear Temple has collapsed as a direct result of the Thai artillery bombardment." It did not say how large the wing was.

Built between the 9th and 11th centuries, Preah Vihear is dedicated to the Hindu diety Shiva and revered partly for having one of the most stunning locations of all the temples constructed during the Khmer empire — the most famous of which is Angkor Wat. It sits atop a 1,722-foot (525-meter) cliff in the Dangrek Mountains about 150 miles (240 kilometers) north of the Cambodian capital.

UNESCO calls the site "an outstanding masterpiece of Khmer architecture." The Khmer empire, which once encompassed parts of Thailand and Vietnam, shrank to the size of present-day Cambodia. The country was plunged into civil war, and the temple fell into disrepair.

Thai army spokesman Col. Sansern Kaewkamnerd dismissed reports of damage to the temple as "propaganda," but said Sunday’s fighting was more intense than the previous two days.

Tensions have risen in recent days because of demonstrations in the Thai capital, Bangkok, demanding that the government oust Cambodians from the area near the temple.

Thailand’s Prime Minister Abhisit Vejjajiva called earlier Sunday for a peaceful solution to the border dispute, but warned that Thai soldiers would defend national sovereignty if attacked.

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Associated Press writers Thanyarat Doksone, Todd Pitman and Jocelyn Gecker also contributed to this report.