Thailand-Cambodia border tension escalated on Monday as the Thai military launched air attacks along the border, following recent clashes that led to several deaths and injuries on both sides.

The two neighbors opened fire over the weekend at the border region in the Ubon Ratchathani Province, which led to the death of a Thai soldier, the Royal Thai Air Force said on Monday.

Thailand has deployed F-16 fighter jets to strike military targets in several areas to suppress Cambodian fire-support positions, after those positions had used artillery and air-dropped munitions against Thailand, it said.

The air force's spokesman, Jackkrit Thammavichai, said Cambodia had mobilized heavy weaponry, repositioned combat units and prepared fire-support activities that could escalate military operations and pose a threat to the Thai border.

All missions were executed with caution, targeting only military infrastructure, weapons depots, command centers and logistical routes assessed as direct threats, he said.

However, Cambodia denied details of the Thai statement.

"Cambodian forces have not undertaken any action that violates the ceasefire agreement," Cambodia's Defense Ministry said. It denied that heavy weapons were mobilized.

The attacks killed at least four Cambodian civilians, Agence France-Presse reported.

Defense Ministry spokeswoman Maly Socheata said on Monday that the Thai military opened fire on civilians, state news agency AKP reported.

The recent attacks took place following numerous provocative actions by the Thai military, despite both sides having stated firmly they were still committed to respecting the truce deal and adhering to peaceful dispute resolution in line with international law, she added.

Thailand's Prime Minister Anutin Charnvirakul said on Monday afternoon that the military will "take action in all necessary cases according to the situation, and will carry out any additional military operations that may be required".

The Thai Foreign Ministry said the clash has led to the evacuation of 400,000 residents in four border provinces, and the closure of 600 schools and several hospitals in five border provinces.

In Cambodia, the education ministry announced the closure of 377 schools across four provinces bordering Thailand, citing tensions that have halted education for about 78,600 students and 3,197 teachers.

Restraint urged

Senate President Hun Sen urged frontline troops to exercise restraint amid renewed armed conflict. He called on authorities at all levels to assist people who have fled from dangerous border areas to safe zones.

At a news briefing on Monday, Pipat Luengnaruemitchai, an economist at Kiatnakin Phatra Securities in Bangkok, warned of the potential damage the border conflicts could cause to the tourism industry, local news portal The Nation reported.

Trade disruption is the most immediate economic channel affected by the border tensions, Pipat said. The fighting also creates substantial political and trade uncertainty, which may affect diplomatic matters and current trade negotiations with other countries, he added.

Puangthong Pawakapan, a professor at the Faculty of Political Science at Chulalongkorn University in Bangkok, urged both Thailand and Cambodia to restore calm and called for neutral observers to closely monitor the situation and prevent either side from easily reigniting the conflict.

"Civil society in both countries must push their governments to find a serious solution to this conflict, as it benefits no one — especially border communities and the long-term economic stability of both nations," she said in a Facebook post on Monday.

Xinhua contributed to this story.

yangwanli@chinadaily.com.cn