Swedish-Chilean national Zaida Catalan and her American colleague Michael Sharp were investigating reports of mass graves in central DR Congo when they were shot dead

Two UN experts who were killed six months ago in the Democratic Republic of Congo were deliberately misled about the safety of the place where they were shot dead, French radio said Wednesday.

In an investigative report published on its website, Radio France International (RFI) suggested the pair may have been set up.

Zaida Catalan, a Swedish-Chilean national and Michael Sharp, who held US nationality, were killed in March while probing reports of more than 40 mass graves in the war-torn central region of Kasai.

Their bodies were found 16 days later. Catalan had been decapitated.

Violence erupted in Kasai in August 2016 following the killing of a local tribal chief called the Kamwina Nsapu, prompting deadly clashes between his followers and the military.

In its report, RFI published the transcript of a conversation the pair had on the eve of their death with a Kamwina Nsapu follower speaking Tshiluba, which was translated by several other people into French.

"At least three of the participants intentionally misled the two experts about the level of security in Bunkonde," RFI said of the area where they were killed.

- 'Not translated' -

At one stage, the main speaker -- an elderly healer called Francois Muamba -- tries to discourage them from going to Bunkonde, raising the possibility of an ambush.

But his words "were not translated", RFI said.

Instead, they were told: "As far as guarantees go, you can go to Bunkonde because there's nothing going on there."

RFI said the translator was "currently working with the (government) department of migration", describing him as "close to the new Kamwina Nsapu who was backed by the authorities".

Another person who was party to the conversation and said to be close to the Kamwina Nsapu militia, was "an intelligence agent" who was "in charge of supervising the two experts' mission in Bunkonde."

- State actors? -

A report compiled by UN experts in June also said the pair had spoken to members of the clan leader's family on the eve of their departure from Kananga on March 12, citing as evidence an audio tape of the meeting they had obtained.

It described their murder as a "premeditated setup", saying that members of the state security services may have been involved.

The Congolese authorities have said the pair were killed by militia members, with a UN inquiry published last month reaching the same conclusion.

RFI's investigation was led by Sonia Rolley, its former correspondent in the country, whose press accreditation has not been renewed by Kinshasa since May.

On the day of the murder, she was working just a few kilometres (miles) from the scene of the crime.

"If she has evidence, she should bring it to the judicial authorities," government spokesman Lambert Mende told AFP, saying a failure to do so would be "a serious violation of criminal proceedings."

Kinshasa says nine out of 16 suspects have been arrested, with four of them going on trial before a military tribunal in Kananga on June 5.

"There is a trial under way. We cannot comment while this is ongoing," said a spokesman for MONUSCO, the UN's peacekeeping mission in the country.

Over the past year, the wave of violence in Kasai has claimed more than 3,000 lives, and displaced an estimated 1.4 million people, with rights groups citing evidence of extrajudicial killings, rapes, torture and the use of child soldiers.