Ukraine's jailed opposition leader and former premier Yulia Tymoshenko has been on a hunger strike since Friday to protest her treatment by prison wardens and doctors, her lawyer said.

"Yulia Tymoshenko has declared a hunger strike," Interfax quoted Serhiy Vlasenko as saying outside her prison in the eastern city of Kharkiv where Tymoshenko has been jailed since last year on abuse of office charges.