Cambodia's prime minister has called for a UN buffer zone in a disputed area on its border with Thailand.
Hun Sen made the appeal as Cambodian and Thai troops exchanged fire around the 11th-Century Preah Vihear temple for a fourth day.
At least five people were killed in clashes over the weekend and thousands of civilians have fled the area.
UN Secretary General Ban Ki-moon has called on both sides to "exercise maximum restraint".
It has been the most sustained fighting between the two neighbours in years.
The clashes have claimed the lives of two soldiers and a civilian from Cambodia, one Thai soldier and a Thai civilian - though the two countries' media have reported differing casualty figures.
Each country accuses the other of encroaching on its territory and of firing first.
The Cambodian government says a Thai bombardment has damaged a wing of the ancient temple - but Thai officials have reportedly rejected the claim.
Mr Hun said on Monday that the confrontation was "threatening regional security".
"We need the United Nations to send forces here and create a buffer zone to guarantee that there is no more fighting," he said during a university graduation ceremony in the capital, Phnom Penh.
"We will go to the UN Security Council whether you like it or not."
Mr Hun noted that Cambodia had contributed to UN missions in Africa, according to quotes on Xinhua.
He had already asked the UN Security Council to help stop what he called Thailand's "repeated acts of aggression" against his country, and asked for an emergency meeting of the Security Council.
Thailand sent its own letter to the Security Council to protest against "repeated and unprovoked armed attacks by Cambodian troops".
The Thai foreign ministry reiterated on Monday that Thai troops had acted in "self-defence".
"Thai troops had exercised maximum restraint and used force only as necessary, in a manner proportionate to the threat against them," a ministry statement said.
"Additionally, fire was directed only at military targets from where the attacks were launched by Cambodian troops."
The foreign ministry also said more than 6,000 Thais from the border area had been evacuated.
At the UN, Mr Ban's office said he was "deeply concerned".
"The secretary-general appeals to both sides to put in place an effective arrangement for cessation of hostilities and to exercise maximum restraint," it said.
No injuries were reported after the latest, brief exchange of fire on Monday.
The International Court of Justice ruled in 1962 that the Preah Vihear temple belonged to Cambodia.
Thailand accepts Cambodia's sovereignty of Preah Vihear, however the land surrounding the temple is still disputed.
In 2008, Cambodia was awarded Unesco World Heritage status for the temple, which further angered Thailand.
The most recent tension was sparked last week, when a Cambodian court sentenced two members of a Thai nationalist movement to up to eight years in prison after finding them guilty of espionage.
The two were among seven Thai politicians and activists charged with illegal entry by Cambodia after crossing into a disputed border area in December.
The case has outraged Thai nationalists.
Members of the People's Alliance for Democracy (PAD), known as the "yellow-shirts", have been staging protests in Bangkok, urging the government to take a tougher line over the border issue.