KHARKIV, Ukraine (Reuters) - Ukraine's former prime minister Yulia Tymoshenko went on trial on Thursday and faces up to 12 more years in prison if convicted of fresh graft charges, in a case that once again drew harsh criticism from an attending Western human rights official.

She refused to attend Thursday's hearing citing poor health.

A key opponent of President Viktor Yanukovich, Tymoshenko was sentenced last October to seven years in prison for abusing her powers as prime minister. The case soured Ukraine's ties with the West which saw it as politically motivated.

In the new trial, she is accused of tax evasion, fraud and attempted theft related to her work as the head of major gas trading company UES, now defunct, in the 1990s.

Tymoshenko has denied any wrongdoing in both cases, dismissing them as part of a campaign of repression against the opposition by Yanukovich's government.

"There is no doubt that the charges are politically motivated," Francois Zimeray, the French ambassador for human rights, told reporters after attending the hearing in the city of Kharkiv where Tymoshenko is in prison.

The European Union has warned Ukraine that its members would not ratify key bilateral agreements on political association and free trade while Tymoshenko remains in prison.

But Yanukovich has refused to intervene, indicating he could only pardon Tymoshenko once all trials against her are over.

Ukrainian prosecutors are also investigating Tymoshenko over what they say was her possible involvement in the 1996 contract killing of a parliament deputy, a charge she also denies. Continued...