KIEV, April 26 (Reuters) - One of the international observers being held by pro-Russian separatists in the eastern Ukrainian city of Slaviansk needs urgent medical care, Ukraine's state security service said on Saturday.
"Today the official representatives of the OSCE (Organisation for Security and Cooperation in Europe) are being held in inhuman conditions in the basement of the terrorists' headquarters," the service said in a statement on its Internet site.
"Among those detained is a person who needs immediate medical help." The statement said Ukrainian security services were ready to provide medical assistance, but the separatists had rejected this offer.
"The terrorists plan to use the hostages as a human shield," the statement said.
It said the detention of the observers was planned and coordinated by a Russian citizen who Kiev says is a Russian special service operative. Russia denies that it has any of its troops or agents in eastern Ukraine.
"Ukraine underlines the extreme necessity for the Russian Federation to distance itself from, and condemn, the terrorist actions in Slaviansk, and to support, as one of the OSCE's members, the immediate and unconditional release of the hostages and the provision of medical and other care." (Reporting by Pavel Polityuk; Writing by Christian Lowe)