KIEV (AP) — The mayor of Ukraine’s second-largest city was shot in the back and pro-Russia insurgents seized more government buildings Monday as the US hit Russia with more sanctions for allegedly fomenting the unrest in eastern Ukraine.

One presidential candidate said the mayor was deliberately shot in an effort to destabilize the entire city of Kharkov.

Armed insurgents tacitly backed by Moscow are seeking more autonomy in the region — possibly even independence or annexation with Russia. 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.

Ratcheting up the pressure on Russian President Vladimir Putin, President Barack Obama’s government levied new sanctions Monday on seven Russian officials and 17 companies with links to Putin’s inner circle. The US also revoked licenses for some high-tech items that could be used by the Russian military.

In Brussels, the European Union moved Monday to add 15 more officials to its Russian sanctions list to protest Moscow’s meddling in Ukraine. That decision, reached by the ambassadors to the EU’s 28 nations, was being formally confirmed by the EU’s governments and was expected within hours, officials told The Associated Press.

Hennady Kernes, the mayor of Kharkov, was shot in the back Monday morning while cycling on the outskirts of the city and underwent surgery, city hall said. He was reported by the hospital to be in “grave, but stable” condition.

Officials have not commented on who could be behind the attack — but Kernes was a man who could have angered both sides.

Kernes’ friend and former Kharkov governor, Mykhailo Dobkin, told journalists the attackers were aiming at Kernes’ heart and wanted to kill him in an effort to destabilize the city of 1.5 million. Dobkin is among several candidates running in Ukraine’s May 25 presidential election.

“If you want to know my opinion, they were shooting not at Kernes, but at Kharkov,” he said.

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 who sent activists to Kiev from eastern Ukraine to harass those demonstrators.

But he has softened his stance toward the new Kiev government. At a meeting of eastern Ukrainian leaders and acting Prime Minister Arseniy Yatsenyuk this month, Kernes insisted he does not support the pro-Russia insurgents and backed a united Ukraine.

Kharkov is in eastern Ukraine, where pro-Russia gunmen have seized government buildings and police stations, set up roadblocks and staged protests to demand greater autonomy or even annexation by Russia. But unlike the neighboring Donetsk region, Kharkov has been largely unaffected by the insurgency and Kernes has been credited for this. Its administration building was briefly seized earlier this month but promptly cleared of pro-Russia protesters.

The Russian Foreign Ministry said the attack on Kernes, along with other events, “indicates that it isn’t possible to speak of any ‘peaceful’ pre-election campaign in Ukraine.”

On Monday, pro-Russia militants wearing masks gained another foothold in east Ukraine, seizing a city hall building and police station in the city of Kostyantynivka, 160 kilometers (100 miles) from the Russian border. The city is 35 kilometers (22 miles) south of Slovyansk, a major city that has been in the hands of insurgents for more than three weeks.

After the seizure, about 15 armed men guarded the city hall building. Some posed for pictures with residents while others distributed St. George’s ribbons, the symbol of the pro-Russia movement.

Moscow has repeatedly pushed for a referendum on federal autonomy in Ukraine, but Kiev and its Western allies have refused, accusing Russia of fomenting separatist sentiment in an attempt to foil the May presidential vote.

However, Justice Minister Petro Petrenko said the parliament in Kiev would debate the idea of a referendum on Tuesday, Interfax news agency reported.

The increasingly ruthless pro-Russia insurgency, meanwhile, is turning to an ominous new tactic: kidnapping. About 40 people are being held hostage in makeshift jails in Slovyansk — including journalists, pro-Ukraine activists and seven military observers from the Organization of Security and Cooperation in Europe, Ukraine’s Security Service said Monday.

The German government called Monday for the immediate release of the European military observers, who were detained Friday on allegations they were spying for NATO.

Pro-Russia militants in camouflage and black balaclavas paraded some of the captive military observers before the media on Sunday. They also showed three Ukrainian security guards bloodied, blindfolded and with their arms bound.

On the other side, Russia’s foreign ministry said Ukraine’s effort to detain pro-Russia activists had become a “witch hunt” that involved the “mass persecution of dissenters.” The foreign ministry also said it had information that Ukraine was building mass temporary detention centers for these prisoners.

“Those structures being constructed very much remind one of fascist concentration camps,” the Russian statement said.

Copyright 2014 The Associated Press.