KIEV, Ukraine - Ukraine has filed new criminal charges against imprisoned former Prime Minister Yulia Tymoshenko, defying Western pressure to release her.

The State Tax Service said Friday it charged Tymoshenko with concealing $165 million worth of foreign currency revenues, and embezzling and evading taxes worth $5.8 million while she headed an energy company in the mid-1990s. Tymoshenko's office rejects the charges.

Tymoshenko, Ukraine's top opposition leader, was sentenced to seven years in prison last month on charges of overstepping her authority while negotiating a natural gas import contract with Russia in 2009. The U.S. and the West have condemned the verdict as politically motivated.

Tymoshenko is the subject of at least three other criminal investigations.