Foreign Minister of Laos Thongloun Sisoulith has said the use of cluster bombs during February’s deadly clashes between Thailand and Cambodia was a “serious concern”, calling them “horrific weapons”.

During the border fighting around Preah Vihear , Thailand used 155-milimetre Dual Purpose Improved Conventional Munition: large shells launched from the ground that split open and release dozens of smaller bomblets across a wide area.

While the United Kingdom-based Cluster Munition Coalition says the weapons are internationally recognised as cluster bombs and banned under the 2008 Convention on Cluster Munitions, Thailand last week claimed they were not.

Thongloun Sisoulith, the Laotian Foreign Minister, urged all countries to sign and adhere to the 2008 convention banning the use of cluster bombs in a statement released on Friday by the CMC.

“It is of serious concern to learn of the recent use [of cluster munitions], and in particular on South East Asian soil, already so heavily impacted by these horrific weapons,” said Thongloun, who hosted an international meeting of state parties last year in support of the 2008 treaty. The Thai Foreign Ministry also issued a statement on Friday, reiterating its claim that it does not see DPICM as a cluster bomb.

Spokesman Thani Thongphakdi said in the statement that the Thai ambassador to the United Nations in Geneva, who the CMC said confirmed the use of cluster bombs during a meeting, had been “misrepresented”. He also claimed that the Thai military used DPICM to retaliate for Cambodian rocket fire.

“Thai troops had exercised maximum restraint, on the basis of necessity, proportionality, and in strict compliance with the military code of conduct and rules of engagement, taking the utmost caution to avoid civilians,” Thani said.

Neither Cambodia nor Thailand has signed the 2008 convention, which has been signed by 108 states and ratified by 56.

The treaty prohibits the use, transfer and stockpile of the deadly weapons because of the long-term threat they leave to civilians.

In the midst of the fighting at the border, two policemen died and another eight were injured on February 6 when an unexploded submunition detonated in the hands of a policeman in Preah Vihear province’s Svay Chrum village, police said after the incident.