SLOVYANSK, Ukraine (AP) -- Pro-Russian militants in camouflage fatigues and black balaclavas paraded captive European military observers before the media on Sunday, hours after three captured Ukrainian security guards were shown bloodied, blindfolded and stripped of their trousers and shoes, their arms bound with packing tape.
The provocative displays came as the increasingly ruthless pro-Russian insurgency in the east turns to kidnapping as an ominous new tactic.
Dozens of people are being held hostage, including journalists and pro-Ukraine activists, in makeshift jails in Slovyansk, the heart of the separatists' territory, as the pro-Russian insurgents strengthen their control in defiance of the interim government in Kiev and its Western supporters.
Speaking in deliberate and clipped phrases, Col. Axel Schneider of Germany, speaking on behalf of the observers, insisted they were not NATO spies, as claimed by the insurgents, but a military observation mission operating under the auspices of the Organization of Security and Cooperation in Europe.
"We are not fighters, we are diplomats in uniform," he said, noting that his unarmed team included an officer from Sweden, which is not a NATO member.
The observers appeared nervous as they were escorted by the masked armed men into the Slovyansk city hall for the news conference.
Referring to himself and his team as "guests" under the "protection" of the city's self-proclaimed mayor, Schneider said they were being treated as well as possible under the circumstances.
"The mayor of this city granted us his protection and he regarded us as his guests," Schneider told journalists. "I can tell you that the word of the mayor is a word of honor. We have not been touched."
Schneider said his group, which was detained by pro-Russian militiamen outside Slovyansk on Friday, was initially kept in a basement before being moved Saturday.
"Since yesterday, we have been in a more comfortable room, which has been equipped with heating. We have daylight and an air conditioning unit," he said, "All our officers, including the interpreters, are healthy and well."
The spectacle of accredited diplomats being presented to the media as what Slovyansk's insurgency-appointed mayor, Vyacheslav Ponomarev, has described as "bargaining chips" provoked disgust in European capitals.
German Foreign Minister Frank-Walter Steinmeier condemned it as "revolting" and a violation of the men's dignity. Four members of the team are German.
One of the observers, Swedish officer Maj. Thomas Johansson, was released later in the day "on humanitarian grounds as he has a mild form of diabetes," said Stella Khorosheva, a spokeswoman for the Slovyansk mayor. The officer got into a car with OSCE representatives outside city hall and drove off with them.
Schneider, who was speaking before the Swede was freed, said he had no information about when they would be released and that this was a matter for diplomats of their countries. The group also includes officers from Poland, Denmark and the Czech Republic.
The German colonel said he understood that the Slovyansk mayor could use the observers as a bargaining chip.
"Our presence here in Slovyansk is for sure a political instrument for the decision makers here in the region and the possibility to use it for negotiations," Schneider said. "It's logical in the eyes of Mayor Ponomarev that he can use us to present his positions."
Ponomarev said Saturday the European observers could be released in exchange for jailed pro-Russia activists.
Overnight Saturday, the insurgents captured three Ukrainian security guards, who were shown to Russian journalists in the security service headquarters in Slovyansk. Barely concious and showing signs of sustained beating, they sat with their heads bowed.
In footage obtained by The Associated Press, Russian reporters could be heard haranguing the officers, who were able to reply only in faintly audible monosyllables.
Igor Strelkov, who has been identified as the commander of the armed insurgents, said the three Ukrainian officers were on a mission to seize leaders of the pro-Russia force when they were captured.
Ukraine's Security Service confirmed that its officers had been seized by armed men and said they were on a mission to detain a Russian citizen suspected in the killing of a Ukrainian parliament member.
Also on Sunday, several hundred pro-Russia activists stormed the television broadcasting center in Donetsk, the regional capital of eastern Ukraine, to demand that Russian state channels be put back on the air. The Kiev government last month blocked broadcast of the Russian channels, which serve as propaganda tools for the Kremlin.
The crowd included several dozen men wearing camouflage fatigues and face masks, the standard uniform of the pro-Russia forces that have seized government buildings in at least 10 cities in eastern Ukraine.