A military court in the Democratic Republic of Congo convicted nine soldiers on Monday of the mass rape of more than 50 women in the country's troubled east and imposed prison sentences of up to 20 years.

The attacks happened on New Year's Day in the town of Fizi, in the unstable province of South Kivu, where abuses are rife amid clashes between the army, local and foreign rebels and militia fighters.

Commanding officer Lieutenant-Colonel Kibibi Mutware, a former rebel, was thrown out of the army and sentenced to 20 years in prison for the attacks. Eight of his men were also dismissed and got sentences from between 10 and 20 years, according to a Reuters witness in the courtroom.

One soldier was acquitted and another, who is 16, will be tried in a juvenile court.

The trial took place in the nearby town of Baraka and lasted more than ten days.

It was seen as a major test of whether the authorities are serious about ending impunity in Congo, where violence simmers eight years after the last war officially ended and in the approach to a presidential election due later this year.

The United Nations has called Congo the rape capital of the world; mass rapes are frequent and armed men, often from government units, are seldom held accountable.