Pro-Russia forces in Ukraine offer to free European team in prisoner swap

A pro-Russian insurgency leader in eastern Ukraine said Saturday that foreign military observers, detained by the insurgents as suspected NATO spies, could be released in exchange for jailed pro-Russian activists, as tensions in the country’s east remained high. Ukraine’s acting prime minister said Russian military aircraft had violated his country’s airspace, and Western powers moved closer to punishing Russia with more sanctions.

Outside Slavyansk – a Ukrainian city some 90 miles west of Russia that has been a hotbed of activity for pro-Russian armed groups in the last month – Ukraine government forces continued operations to form a security cordon as they attempted to quell unrest that threatens to derail planned elections on May 25.

Vyacheslav Ponomarev, self-proclaimed people's mayor of Slavyansk, described the detained observers from the Organization of Security and Cooperation in Europe (OSCE) as "captives." He said that they were officers from NATO member states.

"As we found maps on them containing information about the location of our checkpoints, we get the impression that they are officers carrying out a certain spying mission," Ponomarev said.

Pro-Russian militiamen detained the eight-member, German-led OSCE team on Friday. Germany's Defense Ministry said that it had had lost contact with the team, and that the mission had included five Ukrainians.

Tim Guldimann, the OSCE's special envoy for Ukraine, told German public radio WDR on Saturday that "efforts are being made to solve this issue." He declined to elaborate.

German Foreign Minister Frank-Walter Steinmeier called Russian Foreign Minister Sergey Lavrov late Friday to press for the release of the observers.

In a statement issued Saturday, Russia's Foreign Ministry said it was taking "all measures to resolve the situation," and blamed the authorities in Kyiv for failing to keep the team safe.

"The security of the inspectors is wholly entrusted to the host party," the statement said. "Hence it would be logical to expect the current authorities in Kiev to resolve preliminary questions of the location, actions, and safety of the instructors."

Meanwhile, during a trip to Rome to meet with Pope Francis and Italian Premier Matteo Renzi, Ukraine's acting Prime Minister Arseniy Yatsenyuk held a briefing with reporters on Saturday and lashed out at Moscow, saying Russian military aircraft had violated Ukrainian airspace late on Friday.

"The only reason is to provoke Ukraine to strike a missile and to accuse Ukraine of waging a war to Russia," he said, and asked Russia "not to provoke and not to support Russian-led terrorists ... in eastern and southern Ukraine. We ask Russia to leave us alone."

A Russian Ministry of Defense spokesman on Saturday denied claims – first raised by the United States on Friday – that its aircraft had crossed the border with Ukraine.

The U.S. and other nations in the Group of Seven said in a joint statement released Friday night by the White House that they plan to impose additional economic sanctions on Russia in response to its actions in Ukraine.

The West has accused Russia of using covert forces to encourage unrest in Ukraine, and says Moscow has done nothing to pressure pro-Russian militias to halt their occupation of police stations and government buildings in at least 10 cities across the region.

Condemning Russia's annexation last month of the Ukrainian Black Sea region of Crimea, the G-7 said: "We will now follow through on the full legal and practical consequences of this illegal annexation, including but not limited to the economic, trade and financial areas."

A European Union source said ambassadors from 28 EU member states would meet on Monday in Brussels to agree on a "list of 'Stage 2' sanctions" to add to the list of Russian officials and pro-Russian leaders in Ukraine who have already been sanctioned with EU asset freezes and travel bans.

Al Jazeera and The Associated Press