MOSCOW -- European military observers who were held more than a week by insurgents in eastern Ukraine walked free Saturday, with Kiev insisting the release proves Russia is fomenting unrest in Ukraine -- as Moscow touted the insurgents as courageous humanists.
The latest battling narratives came a day after dozens of protesters died while trapped in a horrifying fire in Odessa, hundreds of miles away. Kremlin spokesman Dmitry Peskov said the deaths show Ukraine's acting leaders are "up to their elbows in blood," while authorities in Kiev blamed pro-Russia provocateurs.
The incidents highlight the intractability of Ukraine's crisis, in which pro-Russia insurgents have seized government buildings in about a dozen cities and towns in the east and Ukrainian forces have tried to regain control in a limited military offensive. Looming on the other side of the border are tens of thousands of Russian troops, whom Kiev fears are waiting for a pretext to invade.
A pact struck among Russia, Ukraine, the European Union and the United States in mid-April aimed to resolve the crisis emphasized the importance of an observer mission from the Organization for Security and Cooperation in Europe. But the mission's prospects became clouded a week later, when eight of its military observers and five accompanying Ukrainians were detained by insurgents in the city of Slovyansk, the crucible of unrest in the east. The insurgents alleged the observers were spying for NATO and carrying suspicious material; one from non-NATO member Sweden was released two days later, but the rest remained in custody until Saturday.
The insurgents' leader in Slovyansk, Vyacheslav Ponomarev, was quoted by Interfax news agency as saying he ordered the release because of increasing insecurity in the city. In recent days, at least four Ukrainian soldiers were killed on the city's outskirts -- two of them when helicopters were shot down -- and at least 10 civilians have been killed, according to Mr. Ponomarev.
Mr. Ponomarev later told The Associated Press that the OSCE observers "are not being released -- they are leaving us, as we promised them."
One of the released observers, German Col. Axel Schneider, told AP that the 12 detainees held up well. Those held included three other Germans and a soldier each from the Czech Republic, Denmark and Poland.
The non-Ukrainians were flown late Saturday to Berlin, where they were reunited with their families.
The release negotiators included Vladimir Lukin, a representative of Russian President Vladimir Putin. Mr. Lukin was brought in as part of an initiative led by Thorbjorn Jagland, the head of the Council of Europe, a European human-rights body, according to COE spokesman Daniel Hoeltgen.
Mr. Lukin was quoted by the Russian state news agency RIA Novosti as saying the release was "a voluntary humanitarian act."
Although Russia denies it is encouraging or directing the insurgents, Ukrainian Foreign Ministry said in a statement that the release "was made after unambiguous instructions had been received from the Russian authorities, which yet again shows the extremists are subordinated to Moscow."
The Russian Foreign Ministry, however, emphasized that the release was a decision of the insurgents who have taken control of Slovyansk and called it "testimony of the courage and humanism of the defenders."
Despite the release, tensions in Ukraine heightened sharply after at least 42 people died Friday in clashes between government supporters and opponents in the Black Sea port of Odessa. On Saturday, news reports claimed fighting broke out in the city of Kramatorsk, about 10 miles south of Slovyansk.
The Odessa clash began with street fighting between two sides in which at least three people were reported killed by gunfire, then turned into a conflagration when government opponents took refuge in a building that caught fire after protesters threw firebombs inside.
At least 36 people died in the fire, according to the emergencies ministry. An Interior Ministry statement gave the overall death toll for the day at 42, but did not give a breakdown.
The city's police chief, Petr Lutsyuk, on Saturday issued a statement calling for calm in the city of about 1 million, but hours later he was fired by Interior Minister Arsen Avakov.
Mr. Peskov, the spokesman for Mr. Putin, said the bloodshed demonstrated the acting government's tolerance of or collusion with nationalist extremists and had driven efforts to resolve the crisis into a dead end.
The Ukrainian Foreign Ministry blamed pro-Russia adherents for setting off the clash, didn't mention the fire, and claimed the "events in Odessa show that separatists' subversive activities in Ukraine are doomed to failure."
Odessa, some 330 miles southwest of Slovyansk, had not previously seen significant confrontations in Ukraine's crisis, and the deaths there suggested that violent unrest could spread far from the relatively compact area in the east where it has been concentrated so far.
Odessa is the major city between the Crimean peninsula, which Russia annexed in March, and the Moldovan separatist region of Trans-Dniester where Russia has a military peacekeeping contingent. Some analysts speculate that Russia ultimately aims to take control of a huge swath of Ukraine from Trans-Dniester to the east.