An attack on a military base in eastern Burkina Faso has killed 33 soldiers and wounded 12 others in the latest outburst of violence in the West African country.

The besieged soldiers killed at least 40 “terrorists” on Thursday before reinforcements arrived, the army said in a statement. The attack targeted the military detachment in Ougarou in the Est region.

Burkina Faso’s armed forces have battled rebels since 2015.

More than 10,000 civilians and members of the security forces have died, according to estimates, while at least two million people have fled their homes. One-third of the country lies outside of government control.

The ongoing violence has sparked anger within the military, fuelling two coups last year that led to the ascent of the current leader, Captain Ibrahim Traore, in September.

He has promised to reconquer lost ground, but attacks on security forces and civilians have worsened since the start of the year, inflicting hundreds of deaths.

Traore has said he is committed to a plan by the preceding military administration to hold elections for a civilian government by 2024.

This latest violence comes as the armed forces were accused of indiscriminately killing civilians during anti-insurgency missions.

In a statement issued by Communications Minister Jean Emmanuel Ouedraogo, the government on Thursday expressed “particular concern over reports of killings, in circumstances that remain to be clarified”.

It condemned “these unspeakable and barbaric acts” in the village of Karma in the northern part of the country, and urged investigators to “shed light on the affair, which is repellent to the individual and collective conscience of all men and women enamoured of peace, justice and freedom”.

Survivors and Karma residents have issued a statement saying more than 100 people died, and described a massacre by uniformed men that lasted hours.

Ravina Shamdasani, spokeswoman for the UN’s high commissioner for human rights, has said “at least 150 civilians” may have been killed in the attack.