A lawyer for Ukraine's jailed former Prime Minister Yulia Tymoshenko says she has started a hunger strike after prison guards allegedly beat her.

Tymoshenko, who suffers from a severe spinal condition and needs hospital treatment, was taken last week to a clinic in the eastern city of Kharkiv where her prison is located, but was moved back to prison a day later after refusing treatment.

Tymoshenko's lawyer Serhiy Vlasenko said Tuesday that prison officials had kicked the former prime minister in the stomach while taking her to the hospital by force.

Prison officials declined immediate comment.

The West has condemned Tymoshenko's seven-year prison term on charges of abuse of office as politically motivated.