Three Russian journalists investigating the activities of a Russian paramilitary organization in the Central African Republic were ambushed and killed, their news outlet and local authorities say.

The Russian online news organization Investigation Control Center (TsUR) said in a Facebook post on July 31 that the journalists -- identified as Orkhan Dzhemal, Aleksandr Rastorguyev, and Kirill Radchenko -- were in the country to make a documentary film about ChVK Vagner, a private contractor employing hundreds of mercenaries that has reportedly carried out clandestine combat missions on the Kremlin's behalf in eastern Ukraine, Syria, and elsewhere.

Local and international media have reported that Vagner has been operating in the Central African Republic since Russia delivered light arms to the country's security forces this year and deployed hundreds of military and civilian instructors to train them.

Russian authorities have denied that the Vagner contractors are carrying out their orders.

The group's relationship with the Kremlin is murky, but its leaders have received awards from the Kremlin and its mercenaries have been trained at Russian Defense Ministry facilities. It is reportedly funded by Kremlin-connected businessman Yevgeny Prigozhin.

The Russian Foreign Ministry on July 31 confirmed that three people with identification documents belonging to Dzhemal, Rastorguyev, and Radchenko were found dead and their bodies were brought back to the capital, Bangui.

Russian investigators said they have opened a criminal case to look into the deaths.

Henri Depele, the mayor of the town of Sibut, around 200 kilometers northeast of Bangui, said the journalists were killed late on July 30. Their driver survived the attack.

"According to the driver's explanations, when they were 23 kilometers from Sibut...armed men emerged from the bush and opened fire on the vehicle. The three journalists died instantly," he told Reuters.

TsUR's statement said the journalists flew into the violence-ridden African country on July 27 and that its last contact with them was late on July 29.

Anastasia Gorshkova, deputy editor of the media outlet, told the Russian Dozhd news network that the journalists had tried to enter an estate where members of the security company reportedly stayed, but they were told that they needed accreditation from the country’s Defense Ministry.

On July 30, the journalists planned to meet with a local contact in the town of Bambari, 380 kilometers away from Bangui, Gorshkova said. The road to Bambari runs through Sibut.

The investigative media outlet the journalists worked for is financed by Mikhail Khodorkovsky, a former oil tycoon who spent 10 years in prison following convictions in financial-crimes trials supporters contend were a Kremlin-orchestrated campaign to seize his company's production assets and punish him for challenges to President Vladimir Putin.

He was pardoned by Putin, released, and flown out of Russia in 2010, and now lives in Europe, where he is one of Putin's most vehement critics.

TsUR has published a number of investigations alleging corruption by senior members of Putin's entourage.

Khodorkovsky called the three journalists who were killed "brave men who were not prepared simply to collect documentary material, but wanted to 'feel' it in the palms of their hands.... Rest in peace."

Dzhemal, 51, was a respected Russian military correspondent who covered conflicts around the world. He was seriously injured in Libya in 2011 and published a book in 2008 giving a firsthand account of the five-day Russia-Georgia war.

Rastorguyev, 47, was a prominent documentary filmmaker and a contributor to RFE/RL. He was among the three directors of an award-winning 2013 film about leaders of the Russian opposition.

Radchenko, 33, started his career as a projectionist, but had become a cameraman in recent years. He served as an election observer in Chechnya in March.

The Central African Republic has been riddled by violence, often fought along religious lines between predominantly Christian and Muslim militias, since a 2013 rebellion overthrew then-President Francois Bozize.

Most of the country is beyond the control of the Bangui government, and a 12,000-strong UN peacekeeping mission has struggled to keep a lid on the violence.

With reporting by Reuters, AFP, and The New York Times