The first soldiers to face justice in a huge sex abuse scandal that has rocked the UN and France went on trial in the Democratic Republic of Congo on Monday.

The three Congolese men from the UN's MINUSCA peacekeeping mission in Central African Republic wore blue prison gear as they appeared before the tribunal in Ndolo, a military prison north of the capital Kinshasa.

They are the first troops to be prosecuted in the scandal, which has seen more than 100 victims come forward with horrifying accounts of sexual abuse by UN peacekeepers and French forces.

Another 18 soldiers from DR Congo accused of rape — or attempted rape — of the civilians they were meant to be protecting during a peacekeeping mission in CAR were also present in the court.

"Sergeant Jackson Kikola is being prosecuted for raping a (young girl) of 17 and for not following orders," said public prosecutor Lieutenant Mposhi Ngoy, reading the indictments.

Sergeant major Kibeka Mulamba Djuma faces similar charges, while sergeant major Nsasi Ndazu was charged with disobeying orders and attempted rape. All three pleaded not guilty.

"We want absolute transparency in this trial," the justice minister, Alexis Thambwe Mwamba, told AFP, adding that "a few individuals cannot discredit our army".

Three hearings are scheduled each week, meaning the entire process could take months to complete.

Ida Sawyer, an advocate for Human Rights Watch in the Democratic Republic of Congo, told AFP the trial at Ndolo was "a first, and good, step to end impunity" and called on all countries involved to ensure "real justice".

But Venance Kalenga, who attended the hearing as an observer for Congolese human rights charity ACAJ, said "the absence of victims constitutes a major obstacle in the demonstration of truth".

'SHOCKED TO THE CORE'

The UN said last week its investigators have identified 108 alleged new victims, "the vast majority" of them under-age girls who were raped, sexually abused or exploited by foreign troops.

Secretary-General Ban Ki-moon said he was "shocked to the core" by the allegations made to UN investigators by victims in south-central Kemo prefecture in CAR.

Witness statements gathered by AFP at a camp in Bangui said young girls would have sex with men — some of them soldiers — in exchange for bread, or cash worth the equivalent of less than $1.

AIDS-Free World, a civil society group that tracks peacekeeper sex abuse cases, said three girls told a UN rights officer they were tied up and undressed by a French commander and forced to have sex with a dog.

The girls were then allegedly given about $9 in payment.

The UN's MINUSCA operation, which counts 12,600 foreign police and soldiers, took over from an African Union force in CAR in September 2014 in a bid to end a year of brutal sectarian violence.

Former colonial power France had sent its own intervention force, dubbed "Sangaris", nine months earlier.

Paris has said any French troops convicted would face military discipline and possible criminal penalties.

"We cannot — and I cannot — accept the slightest stain on the reputation of our armed forces or of France," French President Francois Hollande said on Friday.

Under UN rules, the responsibility for investigating and prosecuting peacekeeper sexual abuse lies with the countries that contribute the troops and police to the peace missions.