Sixty South Sudanese soldiers have been tried before a court martial for alleged crimes committed during last month's fighting in the capital Juba, the army spokesman said Monday.

Brigadier-General Lul Ruai Koang told AFP they include looting, murder, shooting and loitering with at least two officers convicted of murder. He said the military is "waiting for presidential approval" before revealing the exact number of those convicted and their sentences.

"They have been tried and the sentences have been passed to the high authorities," Koang said.

However, none of the 60 were charged with rape despite many reported incidents of sex attacks by government soldiers on civilians and aid workers.

Koang said rape victims had failed to come before the court martial, which was neither held in public nor publicised in advance.

"One problem we have been having is lack of evidence. We have been accused left and right by Human Rights Watch and UNMISS [the UN Mission in South Sudan] but unfortunately they have not come forward with evidence for us to move forward against those who have been suspected of committing the crime," Koang said.

"As we speak now we have not received a single complainant who says or confirms that she has been raped so it has been very difficult for us to bring any soldier to book because of lack of evidence," he said.

Koang added that anyone with evidence should bring it to the military.

Survivors of attacks, human rights groups and the UN all reported many rapes during and after an outbreak of fighting between government and opposition forces in the capital last month threatening an already weak peace agreement.

At least 300 people were killed in the latest violence, and more than 60,000 forced to flee the country.

South Sudan's civil war began in December 2013, but a peace deal signed a year ago has so far failed to end the fighting.