Russia said on Friday it planned to send additional military equipment to Central African Republic (CAR) and deploy 60 more instructors to train the country's armed forces, escalating its most significant military foray in Africa in decades.

Russia donated hundreds of weapons and sent 175 trainers to CAR earlier this year to bolster the government's fight against militia groups after receiving an exemption from a United Nations arms embargo.

According to diplomatic and security sources, many of the Russians in CAR are private security contractors and their remit has expanded into mediating negotiations among armed groups, securing mining projects and advising CAR's president.

Russia's activities in CAR are part of a wider push to re-establish influence in sub-Saharan Africa that waned after the Cold War. It has signed military cooperation deals with 19 countries since 2015 and expanded diplomatic and trading ties.

In one of its most extensive comments to date on the subject, Russia's foreign ministry defended its actions in a statement against what it said was "a certain 'jealousy'" by other foreign powers over Russia's role in CAR.

"We believe this kind of position to be counter-productive, particularly in the current context, when constructive cooperation of all international 'players' and not competition or 'zero-sum games' is urgently called for," it said.

"With the knowledge of a relevant UN Security Council committee we are planning to send to CAR an additional 60 civilian instructors and the second part of military purpose products."

According to a confidential memo seen by Reuters, the Security Council's 15-member CAR sanctions committee agreed last month to Russia's request to send the 60 additional instructors, provided they coordinate with CAR's UN peacekeeping mission.

But France, the United States and Britain placed a hold in August on further arms shipments pending confirmation that measures had been taken to secure the previous donation.

Estimates of the total number of Russians in CAR vary widely, from 250 to 1 000. The foreign ministry did not respond directly to questions about the presence of private security contractors.

CAR has faced near-constant armed conflict since 2013, when a mostly Muslim Seleka rebel coalition overthrew then-president Francois Bozize, prompting reprisals from Christian 'anti-balaka' militias.