Lithuania on Tuesday confirmed signs of torture on a prominent Ukrainian anti-government activist and urged an independent probe into the crime which could breach a related United Nations convention.
"Dmytro Bulatov...has clear signs of long term torture and cruel treatment on his body," a Lithuanian foreign ministry said in a statement.
Bulatov, who alleges he was "crucified" and tortured for days by unknown assailants in his homeland, is one of three injured Ukrainian protesters receiving free medical care in Lithuania.
"Ukraine is a party to the United Nations Convention against torture (...) nevertheless, there have been concerns with the implementation of this Convention in the country," it said.
"The European Union has to demand Kiev to launch a thorough and independent investigation into these and other related offences, and take steps to punish the perpetrators," it concluded.
Bulatov, 35, arrived in Vilnius late on Sunday, hours after a Kiev court ruled that he could leave his country for treatment.
He will hold his first press conference in the Lithuanian capital on Thursday.
The leader of the "Automaidan" movement, he organised motorcade protests outside President Viktor Yanukovych's sprawling country estate near Kiev and has been targeted by police.
Bulatov said unidentified kidnappers held him for eight days from January 22.
"They crucified me, nailed me, cut my ear off, cut my face," he said on Ukraine's Channel 5 television shortly after his release last week.
"I can't see well now, because I sat in darkness the whole time."
Images of his bloodied face sparked international outrage, with the European Union's foreign policy chief Catherine Ashton saying she was "appalled by the obvious signs of prolonged torture".
Lithuania played a prominent role in EU efforts to seal a partnership deal with Ukraine. Yanukovych rejected it in November, sparking the wave of at times deadly civil unrest gripping his country.