DAKAR (Reuters) - U.N. investigators Zaida Catalan and Michael Sharp were on familiar ground when they sat down with local leaders in central Congo in March to discuss a widening seven-month-old conflict in the area.

FILE PHOTO: Human skulls suspected to belong to victims of a recent combat between government army and Kamuina Nsapu militia are seen on the roadside in Tshimaiyi near Kananga, the capital of Kasai-central province of the Democratic Republic of Congo, March 12, 2017. REUTERS/Aaron Ross/File Photo

The pair – experienced members of a panel monitoring the sanctions regime in Democratic Republic of Congo for the U.N. Security Council – were meeting members of the Kamuina Nsapu, a local clan, on the sidelines of peace talks with the government in the city of Kananga.

Among other things, they discussed plans to visit the village of Bunkonde, the site of violent clashes, the next day.

The two U.N. workers left Kananga on the morning of March 12. On March 27, their bodies were found in a shallow grave. Catalan had been decapitated.

Congolese government officials maintained for months to reporters that no state agents were involved in the killings and that they did not know that the two experts were in the region, let alone heading to Bunkonde.

But at least one person who helped organize the trip, Jose Tshibuabua, worked for Congo’s intelligence service, the Agence Nationale de Renseignements (ANR), Reuters and Radio France Internationale (RFI) have learned.

The trial of a dozen suspected Kamuina Nsapu militia members started in June but was suspended in October pending the arrival in Congo of four U.N. experts last month to assist with additional investigations.

Phone logs in a confidential prosecutor’s case file compiled for the trial and seen by Reuters and RFI, who jointly reported this story, show that Tshibuabua had frequent contact with a local ANR boss, Luc Albert Tanga Sakrine, before and after the two experts were killed.

Two security sources said that case file was given to a U.N. board of inquiry that concluded militiamen were likely responsible for the killings of Sharp, 34, an American, and Catalan, 36, a Swede.

Tshibuabua and his ties to the ANR were not mentioned in the board’s confidential report to the U.N. Security Council or in the trial, however.

The board said it was unable to establish a motive for state actors to have been involved. But the two experts were conducting investigations in an area where the United Nations has accused Congo’s military of using excessive force against militia and civilians and of digging mass graves.

The top ANR official in Congo, Kalev Mutond, told Reuters and RFI that Tshibuabua was working as a “volunteer informant” for the agency at the time of the meeting, but did not inform ANR officials about his contacts with the two experts.

Since the trial of the militiamen was suspended, Tshibuabua was arrested and charged last week with the murder of Catalan and Sharp and participation in an insurrection, his lawyer, Tresor Kabangu, told Reuters. Kabangu said his client denies the charges and has not worked for the ANR in more than a year.

Government spokesman Lambert Mende now says that authorities have not excluded the possibility that state agents were involved.

“If there is a state agent who was involved, he will be pursued and judged,” Mende said on Dec. 1 after Reuters and RFI laid out the contents of the case file and phone logs.

The U.N. board’s chairman, Greg Starr, declined to say if he had seen the prosecutor’s file or was aware of its contents.

In an emailed answer to questions, Starr said only that the board’s report had a tight deadline and did not include some sensitive information, which was turned over to authorities in the United States and Sweden, because of concerns about leaks.

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“A thorough criminal investigation into a heinous act like this, under these circumstances, could not be accomplished in only three months,” he said.

Congo’s top military prosecutor, Joseph Ponde, declined to respond to questions about why Tshibuabua’s involvement was not raised in the trial, except to say the proceedings are public.

Tanga Sakrine declined to comment. President Joseph Kabila’s deputy chief of staff, Jean-Pierre Kambila, also declined to comment, citing the ongoing trial.

A TENSE RELATIONSHIP

Ties between the United Nations and Congo can be tense, with authorities often accusing the world body of meddling in their sovereign affairs. The U.N. peacekeeping mission, deployed in 1999 to monitor a cease-fire in a long-running war in the east, is the world’s largest with about 18,000 uniformed personnel.

Catalan and Sharp were investigating a new conflict in the central Kasai region. In August 2016, Kamuina Nsapu militiamen in the area rose up to demand government forces withdraw after the local chief, Jean-Pierre Mpandi, was killed.

Up to 5,000 people died in the violence.

On the weekend of March 11, a delegation of about 40 Kamuina Nsapu representatives was in Kananga to talk peace. Members of this delegation met Sharp and Catalan at the Woodland Hotel.

In audio recovered from Catalan’s computer by the United Nations, Tshibuabua describes himself as a Mpandi family member and helps translate from the local Tshiluba language into French for the group’s leader, Francois Muamba. He does not say he works for the ANR.

According to a Reuters translation, Tshibuabua and another person assured Sharp and Catalan in French that their safety would be guaranteed in Bunkonde, even as Muamba warned not to make promises they couldn’t keep.

“We don’t know the situation over there,” Muamba said at one point. He said he did not have control of the local militia in Bunkonde. “Let’s talk about (the situation) near us.”

Tshibuabua continued to assure the U.N. investigators that the militiamen “will not do anything”, adding later: “Here in Kasai, we really guarantee your passage.”

Reuters was unable to reach Muamba for comment.

The prosecutor’s case file includes logs from about 20 phone numbers over various periods from early March to mid-June.

One is from the phone of Tshibuabua and another is from the phone of his cousin Betu Tshintela, who accompanied Catalan and Sharp to Bunkonde as an interpreter. Tshintela claimed in a 2012 job application to the government of Kasai-Occidental province - seen by Reuters and RFI - to have also worked for the ANR.

The government says Tshintela is dead but the United Nations cannot confirm that. Mutond, the top ANR official, could not confirm if Tshintela had worked for the ANR but said he was looking into it.

The phone logs show Tshibuabua was repeatedly in contact with Tanga Sakrine, the provincial ANR chief, around this time. Between March 10 and 12, the two exchanged at least 17 text messages, including five in the afternoon of March 11, shortly after the meeting at the Woodland Hotel, and five around 9 p.m. on March 12, hours after Sharp and Catalan were killed.

Mutond said he asked Tshibuabua three times in an interrogation in the capital Kinshasa whether he informed ANR officials about his contacts with the investigators, and Tshibuabua said no each time.

Reuters and RFI could not independently confirm this.

“I looked Jose Tshibuabua in the eyes and asked him because I myself wanted to have a clean conscience,” Mutond said.

FINAL CALL

Sharp spent three years working in eastern Congo for a Mennonite peace-building organization, trying to persuade rebels to lay down their weapons, before joining the sanctions panel in 2015 as its armed groups expert.

Catalan, the panel’s humanitarian expert, worked for the European Union’s police mission in Congo in 2011-12 and also held posts with the EU in Palestine and Afghanistan.

The phone logs show the last call from Catalan’s phone was to her sister, Elizabeth Morseby, in Sweden at 4:49 p.m.

Morseby told Reuters and RFI she could hear only some male voices in the background and Catalan breathing deeply before the call disconnected. No-one answered when she called back.

Some relatives and rights activists told Reuters and RFI they raised concerns early about possible government involvement because state forces were heavily implicated in rights abuses in Kasai that attracted international attention in the past.

The families and Washington want the United Nations to launch an independent investigation.

A former colleague on the U.N. panel also cast doubt on a video that the government said showed the two being executed by Kamuina Nsapu members. He said the video raised more questions than it answered, for example, why at least one of the alleged assassins gave orders in Lingala, the language of western Congo and the army, rather than the local Tshiluba.

Mende, the government spokesman, countered that many Congolese speak at least some Lingala.

The U.N. board noted theories of “alternate causes of the incident” but cited a lack of motive for government to be involved. It also said Sharp and Catalan failed to heed warnings from U.N. security officials that travel outside Kananga was dangerous.

The FBI has opened an investigation, according to Sharp’s parents, who have met with bureau investigators. The FBI declined to comment.

The Swedish prosecutor’s office is investigating Catalan’s killing but complained in a statement last month that Congolese officials are not cooperating.

Mende said it was up to Swedish authorities to provide information to the Congolese court hearing the case, not the other way around.