More than 5,000 former criminals have been pardoned after finishing their contracts to fight in Russia's Wagner mercenary group against Ukraine, the founder of Wagner, Yevgeny Prigozhin, said on Saturday.

Wagner Group, originally staffed by battle-hardened veterans of the Russian armed forces, took on a much more prominent role in the Ukraine war after the Russian army suffered a series of humiliating defeats last year.

Prigozhin emerged from the shadows and recruited thousands of men from prisons, offering them the chance of freedom in return for serving in some of the most dangerous battles in Ukraine.

"At the present time, more than 5,000 people have been released on pardon after completing their contracts with Wagner," Prigozhin, a close ally of President Vladimir Putin, said in an audio clip posted on Telegram.

Prigozhin said just 0.31% of those pardoned after Wagner service had gone on to commit crime, a figure he said was 10-20 times less than the standard indicators.

Prigozhin, sometimes dubbed "Putin's Chef" for his sprawling catering businesses, is the most powerful of a group of Putin allies who now control what are essentially private armies that recruit top military officers, former spies and convicts.

The United States casts Prigozhin as an oligarch and has sanctioned him for attempts to interfere in U.S. elections and for spreading Russian disinformation across the globe.

Prigozhin, who served nine years in prison in Soviet times for robbery and other crimes before going into business during the 1990s, has admitted interfering in U.S. elections and acknowledged for the first time his role in founding Wagner.

Wagner, which has fought in Libya, Syria, the Central African Republic and Mali, casts itself as the most battle-hardened mercenary group in the world.

It dismisses Western criticism of what it says are sometimes harsh methods and strict discipline by pointing to the use of private military contractors by the United States and its allies around the world.