US citizen Stephen James Hubbard plead guilty to charges of mercenary activity in a Moscow court on Monday, admitting that he had received money to fight for Ukraine against Russia, the RIA state news agency reported.
"Yes, I agree with the indictment," RIA cited him as saying.
Hubbard, 72, was placed in pre-trial detention last week for six months. He faces a sentence of seven to 15 years if convicted.