Last Updated Apr 28, 2014 7:05 AM EDT
KOSTYANTYNIVKA, Ukraine -- The mayor of Ukraine's second-largest city was shot in the back Monday amid spiraling unrest in the country's eastern regions and pro-Russia insurgents seized yet another government building as tensions rose in eastern Ukraine ahead of a new round of U.S. sanctions.
Armed insurgents tacitly backed by Moscow are seeking more autonomy in the region from the interim government in Kiev. In a bid to ratchet up the pressure on Russian President Vladimir Putin, President Barack Obama has promised to levy new sanctions on Russian individuals and companies in retaliation for Moscow's alleged provocations in eastern Ukraine.
Hennady Kernes, the mayor of Kharkiv, was shot in the back Monday morning, his office said. Kernes was said to be undergoing surgery and "doctors are fighting for his life," according to the city hall.
Officials have not commented on the circumstances of the shooting and it was not clear who was behind it. Kernes was a staunch opponent of the pro-West Maidan movement that toppled President Viktor Yanukovych in February and was widely viewed as the organizer of activists sent to Kiev from eastern Ukraine to harass those demonstrators.
But he has since softened his stance toward the new Kiev government and insisted that he does not support the pro-Russia insurgents or any annexation of Ukrainian territory.
Kharkiv is in eastern Ukraine where pro-Russian gunmen have seized government buildings, set up roadblocks or staged protests to demand greater autonomy or outright annexation by Russia.
The building housing the city hall and the city council in Kostyantynivka, just 100 miles from the Russian border, was seized by masked men who carried automatic weapons. About 15 armed men, some wearing a symbol of the pro-Russian movement, guarded the building.
Kostyantynivka is only about 20 miles south of Slavyansk, which has been in insurgents' hands for more than three weeks now.
Since November, Ukraine has been engulfed in its worst political crisis since the 1991 fall of the Soviet Union. Months of anti-government protests in the capital Kiev culminated in President Viktor Yanukovych fleeing to Russia in late February.
Ukraine's acting government and the West have accused Russia of orchestrating the unrest, which they fear Moscow could use as a pretext for an invasion. Last month, Russia annexed Crimea weeks after seizing control of the Black Sea peninsula.
paraded captive European military observers before the media and showed three captured Ukrainian security guards bloodied, blindfolded and stripped of their trousers and shoes, their arms bound with packing tape.
The eight European military observers were taken prisoner by pro-Russian separatists on Friday near the town of Slavyansk. CBS News correspondent Holly Williams was there on Sunday when they were paraded in front of the international media.
German Colonel Axel Schneider and his team appeared tense and unhappy, and there was still no indication Monday when they would will be sent home -- though one of the eight was allowed to leave on Sunday due to a medical condition.
Williams reports that the eight captives said they were being treated well -- but it was impossible to tell if they were under duress.
The provocative displays came as the increasingly ruthless pro-Russian insurgency turns to kidnapping as an ominous new tactic.
Dozens of people are being held hostage, including the seven observers from the Organization of Security and Cooperation in Europe, journalists and pro-Ukraine activists, in makeshift jails in Slovyansk, the heart of the separatists' territory.