Ukrainian ex-prime minister Yulia Tymoshenko.

Kiev, Ukraine - A Ukrainian investigator says jailed former Prime Minister Yulia Tymoshenko's 7-year sentence could be extended, if she is convicted on charges of evading taxes in the mid-1990s.

Tymoshenko, the country's top opposition leader, is presently in jail on abuse of office charges. The West has condemned the verdict as an attempt by President Viktor Yanukovych to sideline a political opponent, and has pressed for the 51-year-olds release.

Mykola Hrabik, an investigator conducting the probe against Tymoshenko, charged Tuesday that she had caused the government millions of dollars in losses by failing to pay taxes while running an energy company.

If convicted, Tymoshenko faces up to 12 years in jail. She would serve her two terms concurrently.

Tymoshenko denies all the accusations, saying Yanukovych is seeking to bar her from politics. - Sapa-AP