One of the eight European military observers held in eastern Ukraine has been released to the Organisation for Security and Cooperation in Europe (OSCE), which had sent negotiators to the region.

A Reuters reporter outside the city administration building in Slovyansk said the man came out, escorted by three unarmed men, got into a white OSCE jeep and drove off.

The man is a Swedish national with diabetes, according to a spokeswoman for the pro-Russian separatists holding the group.

Earlier its members were paraded before the press by their captors who have branded them NATO spies.

Looking sombre, the leader of the mission, Colonel Axel Schneider, said its members were in good health, telling reporters “We have not been touched”.

He added however: “We have no indication when we will be sent home to our countries and to see our families”.

The observers are from Germany, Sweden, Denmark, Poland and the Czech Republic.

Also being held by pro-Russian militia in Slovyansk, a further three captives have been presented as state intelligence officers sent from Kyiv.

Russian TV images showed the men blindfolded, gagged, handcuffed and tied to chairs.

As with the European observer team, rebels have proposed a prisoner exchange, demanding that detained separatists be handed over in return for their release.