Journalists Kirill Radchenko, Alexander Rastorguyev and Orkhan Dzhemal were killed in CAR on Monday.

They were reporting on the so-called Wagner Group -- a company that sends Russian mercenaries to hotspots such as Syria and Ukraine that has been described as Moscow's shadow army.

The journalists were working for a media project launched by Kremlin opponent Mikhail Khodorkovsky, who is living in exile in Britain.

"Russian military specialists do not take any part in fighting in CAR. Their duties are limited to training (local) troops," foreign ministry spokeswoman Maria Zakharova said at a briefing in Moscow.

She added that Russian military specialists were in CAR "on the request of the president of this country."

Zakharova accused some media of doing "everything possible to distort information and the reality concerning the presence of Russian instructors in CAR."

She said currently "there are 175 Russian instructors working in CAR, five of whom are military officers and 170 of whom are civilians."

In March, Moscow announced it had sent to CAR five officers and 170 civilian instructors, whom experts said could be part of Wagner.

"With the help of Russian specialists, 600 African soldiers have been trained and many of them have already started missions aimed at fighting illegal military groups and protecting civilians," Zakharova said.

Since the start of 2018 Russia has deployed military specialists to CAR, sold weapons to its army and provided security for President Faustin-Archange Touadera, whose security advisor is Russian.

Officially, the Russian programme is aimed at strengthening a ramshackle military in CAR, a country where swathes of territory are controlled by armed groups.

But the military mission also boosts Moscow's influence in a struggling strategically-located state whose resources include diamonds, gold, uranium and timber.