WASHINGTON - The US announced its intention on Friday to designate the Wagner Group - a key Russian mercenary organisation - as a "transnational criminal organisation".

The White House announced the plans as part of a wider raft of sanctions aimed at curbing the increasingly powerful mercenary group, which is active across Asia and Africa.

Thousands of mercenaries have been flooding the battlefields of eastern Ukraine, 80% of whom, according to the White House, have been recruited from prisons.

White House national security spokesperson John Kirby accused Wagner of being "a criminal organisation that is committing widespread atrocities and human rights abuses".

Wagner troops, who are becoming increasingly essential to the Russian fight, have been accused of war crimes against Ukrainian civilians.

Recent US reports have also alleged that Wagner has been involved in weapons imports from North Korea, despite UN arms embargoes, to aid the Russian invasion of Ukraine

"[It is] committing atrocities and human rights abuses in Ukraine and elsewhere," said the national security spokesperson on Saturday.

The group’s founder, Yevgeny Prigozhin hit back at the announcement, publishing an open letter to Kirby on Telegram which read: "Dear Mr Kirby, Could you please clarify what crime was committed by PMC Wagner?"

The Wagner group has been instrumental in key conflicts across the Middle East and North Africa since the Arab spring uprisings of 2011, especially in Syria and Libya.

Wagner recruits are widely reported to have committed torture, civilian massacres and body desecrations in Syria dating back to 2017.

The mercenary group has also been expanding its sphere of influence in the Sahel region of West Africa, where military juntas are seeking to shore up power by employing additional troops.