Evidence

Searching found the original Ukrinform report. It relays a Telegram statement from Ukraine's 7th Air Assault Corps. The statement says foreign nationals, including mercenaries from African and Asian countries, are taking part in Russian assaults in the Huliaipole sector. It cites the recent capture of an Indonesian citizen serving in Russia's 39th Separate Motor Rifle Brigade. Ukrinform also gives a figure from Brig. Gen. Dmytro Usov of the POW Coordination Headquarters: Russia has signed contracts with nearly 46,000 foreign nationals from 151 countries. A Euromaidan Press article on an Indonesian recruit looks related. I found no Reuters, AFP, Bellingcat or EUvsDisinfo fact-check of this specific claim, and no independent confirmation of foreign fighters in this sector. The sources are Ukrainian military and media, which are interested parties.