Cambodia wants an "immediate ceasefire" with Thailand, the country's envoy to the United Nations said on Friday, after the neighbours traded deadly strikes for a second day.

A long-running border dispute erupted into intense fighting with jets, artillery, tanks and ground troops on Thursday, prompting the Security Council to hold an emergency meeting on the crisis on Friday.

"Cambodia asked for an immediate ceasefire – unconditionally – and we also call for the peaceful solution of the dispute," said Cambodia's ambassador Chhea Keo following a closed meeting of the Council attended by Cambodia and Thailand.

The envoy questioned how Thailand, a regional military heavyweight, could accuse Cambodia, its smaller neighbour, of attacking it.

"(The Security Council) called for both parties to (show) maximum restraint and resort to a diplomatic solution. That is what we are calling for as well," said Chhea Keo.

None of the other attendees spoke to reporters.

More than 138,000 people have been evacuated from Thailand's border regions, its health ministry said, reporting 15 fatalities – 14 civilians and a soldier – with a further 46 wounded, including 15 troops.

The fighting marks a dramatic escalation in a long-running dispute between the neighbours – both popular destinations for millions of foreign tourists – over their shared 800-kilometre border. (AFP)