SLOVYANSK, Ukraine — The self-appointed mayor of this breakaway city in eastern Ukraine on Sunday displayed eight detained members of a European military observer mission and later released one for health reasons, but otherwise refused to discuss conditions under which the others might go free beyond mentioning a possible prisoner exchange.
In an afternoon of political theater, the de facto public authority here, Vyachislav Ponomaryov, had the detainees led into an auditorium by masked gunmen.
The observers, whom Mr. Ponomaryov has branded as spies, were escorted to seats once used by the city’s administrators. He then yielded the floor to the German officer leading the observers, Col. Axel Schneider, who held a long question-and-answer session with journalists.With erect posture, the colonel began by referring to himself and his team as “guests” under Mr. Ponomaryov’s “protection,” and said the team had suffered no violence at its captors’ hands since being seized on Friday.“We are not prisoners of war,” he said.
But the clearly coercive nature of the display here held the truth of the matter, which Colonel Schneider nodded to toward the end of the conference, saying, “I cannot go home on my free decision.”
He said the observers were performing a diplomatically accredited inspection in a rented bus when they were stopped at a checkpoint about two miles south of Slovyansk, the stronghold of the anti-Kiev armed militias in eastern Ukraine.
The team was held in a basement for one day and then moved on Saturday to better quarters, he said. The observer mission included seven military officers — three from Germany and one each from Czech Republic, Denmark, Poland and Sweden — and a German interpreter, along with five members of the Ukrainian military as escorts.
Colonel Schneider flatly rejected accusations that the observers were spies, and he dismissed claims that the team had carried ammunition and reconnaissance equipment.
His team’s mission, he said several times, had diplomatic status under the so-called Vienna Document 2011 of the Organization for Security and Cooperation in Europe, which allows member nations to invite military observers from other member states to observe internal security conditions.
“I have no overlap with any other action executed in this region,” he said. “It is forbidden.”
The detention of the team has led to intensive diplomatic activity seeking their release.
Germany’s foreign minister, Frank-Walter Steinmeier, condemned what he called the “public display” of the mission members on Sunday, which he said “scandalously violates every rule and standard.” And he called on Russia to use its influence over the separatists in Ukraine to ensure all of the captives would be released unharmed. “It is Russia’s duty to influence the separatists so that they release the members of the O.S.C.E. mission as quickly as possible,” Mr. Steinmeier said in a statement.
Russia’s representative to the security organization has publicly said that the team should be freed.
But Mr. Ponomaryov, who referred to members of the team as “prisoners of the situation,” said he has heard nothing directly from Russia. He gave no timetable for any decisions, but insisted that the observers had been and would be treated well.
“We understand that these are officers before us,” he said. “And as we are also servicemen, we are required to abide by the officers’ code of honor.”
At another moment, Mr. Ponomaryov said the display was intended in part to reassure the observers’ families that the men were in good health. And later in the day, he released one of the observers — a Swedish officer with diabetes, Maj. Thomas Johansson — for health reasons, according to a spokeswoman for Mr. Ponomaryov. (At the end of the conference, Major Johansson noted that he was not ill and had access to medicine during his captivity.)
As the news conference continued, Colonel Schneider gradually expanded on his descriptions of the teams’ circumstances, making clear that its members were detainees.
“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,” he said. “And this is not a surprise.”
He added, “It is logical in the eyes of Mayor Ponomaryov that he can use us to present his positions.”
The antigovernment militias here and their supporters, who seek a referendum that will allow them self-rule, have noted that the interim authorities in Kiev, Ukraine’s capital, have arrested activists or officials on the antigovernment side.
But they have yet to make specific demands for any exchange, beyond Mr. Ponomaryov’s pointing out on Saturday that his own deputy has disappeared and could be in government custody.
The United States has opposed any exchange, and said the detainees should be freed unconditionally.
On Sunday, Mr. Ponomaryov, who was positioned two seats to the colonel’s right, occasionally checking a ringing cellphone, refused to answer questions about a resolution. He did reconfirm that he would consider a prisoner exchange.
When asked by journalists if he thought of the observers as human shields, he said he did not.
“This is nonsense,” he said. “Nonsense. If I gave the word that these people will remain safe, and I provide them capable security, then believe me, I will keep my word.”
Less clear was the status and prospects of five members of the Ukrainian military who had accompanied the observer team.
Colonel Schneider, and then later Major Johansson, said four of these Ukrainians had been held on the first day with the European team, but only two of them were moved with the European officers on Saturday. The conditions and whereabouts of the other three were unknown.
As the back-and-forth inside the sandbagged city administration building continued, a white sport utility vehicle bearing the markings of the O.S.C.E. pulled up outside. Several diplomats stepped out and were escorted into another section of the building by a gunman wearing a black mask.
Mr. Ponomaryov noted that the observers’ release would have to be discussed with diplomats.
“So that these officers feel certain — I told my guests, and I repeat it again — the conditions of their release will be specified with representatives of the O.S.C.E.,” he said. “It will be a separate topic.”
Several minutes after the diplomats arrived, Mr. Ponomaryov abruptly cut short the session and ordered journalists to leave, at one point shouting, “One! Two!” and preparing to shout “Three!” as if trying to compel disobedient children to comply.
The gunmen behind the sandbags led the journalists out into the bright afternoon light of the city’s main public square. There, behind a massive statue of Lenin, a Russian television journalist playfully petted a saddled pony as masked men came and went.