Myanmar¡¯s junta defended its air strikes on a concert, organized by an ethnic minority group, that killed at least 60 people, an act opponents have described as a possible war crime at a time of deepening conflict in the Southeast Asian nation.

Sunday¡¯s aerial attack in Kachin State killed concert performers along with civilians and militia officers and is seen as one of the deadliest since the junta overthrew the civilian government in a coup last year. The strikes appeared to target a concert at a base used for military training by the armed wing of the Kachin Independence Organization, which is aligned with forces loyal to detained civilian leader Aung San Suu Kyi.

While opposition and rights groups have called the attack a likely war violation, the junta argued it carried out the strikes in response to attacks on its forces and this was in line with international rules of engagement.

¡°Security forces are following rules of engagement in accord with the provisions of the Law of Armed Conflict in necessary military operations for combating insurgents to ensure peace and stability of the region,¡± the Office of the Commander-in-Chief of Defence Services said in a statement posted on its website.

The Kachin Independence Organization said the venue is not an outpost of its armed wing but a small shop-lined camp where visitors usually take a break.

¡°The military intentionally attacked to kill people in large numbers,¡± the ethnic army said in a statement. ¡°We will turn this tragedy into a strength for the revolution against the military dictatorship.¡±

Sumlut Gunmaw, deputy chief of Kachin Independence Organization, writing on Facebook said the military treated residents and visitors of the camp as enemies. ¡°Everyone¡¯s sadness and tears will become priceless sacrifices,¡± he said in an open letter to junta chief Min Aung Hlaing.

Violence has flared in Myanmar after the coup with pro-democracy activists fleeing to remote parts of the country to join a revolution against the junta as part of a broader armed conflict that shows no signs of slowing. The military has retaliated with a bloody campaign against those suspected to be standing against their rule.

The attack on Sunday meanwhile has prompted renewed calls to impose stricter sanctions against the regime.

¡°This horrific attack should trigger renewed efforts by concerned states to enforce tougher sanctions on the junta, including cutting off its access to foreign currency revenues as well as arms and aviation fuel,¡± said Elaine Pearson, Asia director at Human Rights Watch.