Pro-Russian rebels in Ukraine have been showing their latest captives to reporters.
Separatists holding the trio in Slovyansk say the men are officers from the state security service in Kyiv, sent on a spying mission to the east.
Russian TV images showed the men blindfolded, gagged, handcuffed and tied to chairs.
Like European military observers seized earlier, a prisoner exchange with detained pro-Russian activists is being demanded for their release.
Pro-Russian rebel commander Igor Strelkov said it would involve an “exchange for our colleagues who have been secretly kidnapped by similar groups to this one. These people were planning to kidnap our people but they got captured.”
The European military observers, who had been travelling with an OSCE mission, are now in their third day of captivity.
The OSCE has sent negotiators to Slovyansk for talks to try to secure the release of the eight-strong group of monitors, branded NATO spies by the separatists.