SLAVYANSK: Russia pledged Saturday to help free a group of international OSCE observers held hostage by pro-Kremlin rebels in eastern Ukraine who accuse them of being “NATO spies.”

“We believe that these people should be released as soon as possible,” Russia’s envoy to the Organization for Security and Cooperation in Europe, Andrei Kelin, told Russia’s state RIA Novosti news agency.

“As an OSCE member, Russia will take all possible steps in this case.”

Russia’s foreign ministry said Moscow was “taking measures” to resolve the situation but did not provide details.

Ukraine’s SBU security service meanwhile said the monitors were being held “in inhuman conditions.”

They said one of the group “urgently” needed medical help but the militants had refused.

“The terrorists are planning to use the hostages as a human shield, effectively terrorizing the whole international community and all members of the OSCE,” the SBU said.

The rebels seized the 13 members of a military observer mission belonging to the pan-European security body on Friday and have refused to set them free.

They were sent to Ukraine to monitor an April 17 accord signed in Geneva between Russia, Ukraine, the United States and the European Union that was meant to de-escalate the dangerous crisis in the ex-Soviet republic.

The OSCE personnel were being detained in the flashpoint town of Slavyansk, which insurgents seized two weeks ago and which is now under siege by the Ukrainian military.

“We arrested some NATO spies... they will be exchanged for our own prisoners. I don’t see any other way they will be freed,” Denis Pushilin, the head of the insurgents’ self-declared Donetsk Republic, told reporters on Saturday.

Slavyansk’s self-styled mayor, Vyacheslav Ponomaryov, also told reporters that they would not be released “until we verify who they are and what aim they came with.”

“They are of course prisoners. They are fine,” he added.

“They have nothing to do with the OSCE. They are military personnel,” he claimed.

He also said they should have asked for “permission” from the rebels to travel in the area.