Soldiers from the insurgent Shan State Army (SSA) claim that shells fired at a military base during a recent assault by Burmese troops may have contained chemical components.

Some 200 Burmese soldiers launched an early morning attack on the 7-Mile base close to Mong Hsu in central Shan state on 3 June. Fighting lasted until evening, according to the SSA’s Colonel Sai Hpa.

He said that two out of four shells fired at the base around midday on 3 June left SSA personnel feeling dizzy. “They could not breathe properly and they vomited,” he said. Burmese troops then were able to take the whole base around 12.30pm, with one SSA soldier who was incapacitated by the attack arrested.

Although use of chemical-laced shells cannot be independently verified, the symptoms described mirror reports of alleged chemical weapons use elsewhere in Burma. A 2005 report by Christian Solidarity Worldwide found circumstantial evidence that the Burmese army had fired mustard gas shells as Karenni Army troops, leaving them vomiting and unable to walk.

Similarly the Karen Human Rights Group (KHRG) said that in both 1992 and 1995 during major offensives against the Karen National Union (KNU), “many [Karen] soldiers… spoke of suffering from ‘dizziness, nausea, vomiting and unconsciousness’ after inhaling the vapours emitted from shells”.

Then in September 2009, the Kachin News Group (KNG) quoted army sources as saying that “mortars laced with chemical ingredients” were being supplied to Burmese battalions in Shan and Kachin state.

One was reportedly fired during fighting in August that year between the Burmese army and an ethnic Kokang group, causing troops and civilians to bleed from the noses and ears, KNG said. The shells were marked with red, yellow and green colouring.

A report on the Shan Herald Agency for News yesterday said that the chemicals allegedly used in the 3 June assault on the SSA base, in which 10 Burmese troops died, produced an abnormal amount of black smoke, while the explosion was quieter than normal mortar shells.

Although the Burmese government signed the Chemical Weapons Convention in 1993, requiring states to destroy all chemical weapons by 2012, it has so far refused to ratify it. US officials have in the past identified Burma as a “probable” chemical weapons possessor.

The Burmese army has been engaged in sporadic bursts of heavy fighting with Shan troops around Mong Hsu since the Shan State Army–North (SSA-N), with whom it agreed to a ceasefire in the mid-1990s, refused demands to become a government-backed Border Guard Force. A fire fight broke out at a Burmese checkpoint in northern Shan state in the evening of 3 July, but so far no casualties have been confirmed.