BANGKOK: Thailand and Cambodia exchanged allegations on Wednesday of breaching a ceasefire deal which has largely halted the open combat that engulfed their frontier.

The nations agreed a truce starting Tuesday after five days of clashes killed at least 43 people on both sides, as a long-standing dispute over contested border temples boiled over into fighting on their 800-kilometre (500-mile) boundary.

Khuon Sudary, president of the National Assembly of Cambodia, urged other countries to help ensure the ceasefire is upheld.

"To prevent the breach of the ceasefire, it is urgent to deploy international observers and inspection teams. Please hold accountable those who violate the ceasefire," she said at the sixth World Conference of Speakers of Parliament in Geneva.

Thailand's foreign ministry said its troops in Sisaket province "came under attack by small arms fire and grenade assaults launched by Cambodian forces" in an offensive that continued until Wednesday morning.

"This represents a flagrant violation of the ceasefire agreement," said a foreign ministry statement.

Thai government spokesman Jirayu Huangsab also reported overnight clashes but said "the Thai side maintained control of the situation" and conditions along the border were "reported to be normal" from 8am (0100 GMT).

On Wednesday, a Cambodian defence ministry official accused Thailand of twice breaching the ceasefire, intended to end fighting which has seen the two countries evacuate a total of more than 300,000 people from the border region.

UN rights chief Volker Turk urged the neighbouring nations to implement their ceasefire deal in full and take rapid steps to build confidence and peace.

"This crucial agreement must be fully respected, in good faith, by both sides, as diplomatic efforts continue, in a bid to resolve the root causes of the conflict," Turk said.

At a temple in Thailand's Surin city serving as a shelter and field kitchen 50 kilometres away from the frontier, volunteer Thanin Kittiworranun said evacuees remain in limbo.