The UN human rights chief said Saturday he had asked several countries to probe allegations of rape and killings by their troops in the Central African Republic following reports of child abuse by French peacekeepers.

A statement said the allegations concerning soldiers from other countries were "very serious" and ranged from executions, abductions to rape.

The appeal came after shocking revelations that French soldiers deployed in the chronically restive, impoverished nation have been accused of sexually abusing children in return for food.

Fourteen French soldiers are under investigation after a group of children alleged troops sexually abused minors at a centre for displaced people in CAR's capital Bangui between December 2013 and June 2014.

Zeid said there had been reports of abuse by soldiers from other countries as well.

"These allegations are extremely disturbing," he said. "Some of these incidents have been at least partly investigated, and some states have apparently sanctioned some of the soldiers involved."

Zeid said apart from asking the countries involved to track down and punish offenders, his office was sending an investigating team to Bangui.

Although France sent police to investigate the claims after receiving an internal United Nations report last August, no children or soldiers were questioned and the information was not made public.

It was only after The Guardian newspaper reported on the affair last month that a full, public investigation was launched.

Both France and the UN have denied there was a cover-up, but a UN official who leaked the report to France last summer was temporarily suspended for disclosing the information.

French and UN peacekeepers were sent to CAR in late 2013 after the country descended into sectarian violence, leaving thousands dead and some 900,000 displaced.

Zeid said some countries had probed rights abuses by their troops following reports from the UN staff in CAR and had taken "preliminary action" including "the sanctioning and early repatriation of some senior ...commanders."

"But this is not sufficient," he said. "The punishment must fit the crime, and some other incidents were reported that may not have been fully followed up on by the states concerned."

"We need to get to get to the bottom of what precisely was done by whom and when," he said.

"There must be accountability for serious crimes no matter who commits them."