DONETSK, Ukraine (CNN) — Gunmen in camouflage occupied a police building in eastern Ukraine, the country’s Interior Ministry said Saturday.
The unidentified armed men arrived at the building in the town of Slaviansk in the morning and took control of it without any casualties.
The Interior Ministry said on its web page that it was sending officials to the scene from the city of Donetsk to assess the situation. The incident comes amid ongoing separatist tensions in the country’s eastern region.
Ukraine’s acting Interior Minister Arsen Avakov warned in a Facebook post that the security forces’ response would be “very strong.”
Avakov on Wednesday vowed the separatist standoff centered on three other eastern cities — Donetsk, Luhansk and Kharkiv — would be resolved within 48 hours, either through negotiations or force. The deadline passed Friday without apparent incident.
Pro-Russian protesters in those cities seized government buildings several days ago and remain barricaded in some of them.
Prime Minister Arseniy Yatsenyuk visited Donetsk on Friday as he seeks to rally those in the region — which has strong ties to Russia — behind the interim government in Kiev ahead of elections due on May 25.
He suggested that constitutional reform could give more power to the regions, though the time frame is short.
“We almost don’t have time to amend the constitution before the presidential election,” he said, adding that they need to move fast so that any new president doesn’t dictate terms.
The United States has accused Russia of fomenting the separatist unrest in its neighbor as a pretext for military intervention.
NATO: ‘All steps necessary’
Russia annexed Ukraine’s southeastern Crimea region last month, following a referendum condemned as illegal by Kiev and the international community, and the West fears it may next seek to enter eastern Ukraine.
The United States and NATO estimate there are up to 40,000 Russian troops near the border. Russia insists they are there on military exercises and that it has no plans to invade.
NATO Secretary General Anders Fogh Rasmussen urged Russia on Friday to pull back its troops from the border area.
Russia should contribute “to a de-escalation of the situation” and engage in a direct dialogue with the Ukrainian government, he said during a visit to Sofia, Bulgaria.
NATO is “not discussing military actions” but is focused on protecting its allies, and it “will take all steps necessary to make sure that this collective defense is effective,” Rasmussen said.
Meanwhile, the organization is reinforcing support to its allies, “from the Baltic to the Black Sea,” to deal with the instability created by Russia, Rasmussen said via Twitter.
NATO released additional satellite images Friday purportedly showing the Russian military buildup and rebutted Russian claims that other satellite photos released a day earlier were outdated. NATO said the photos were recent, gathered between late March and earlier this month.
“It is clear that the military buildup of forces occurred in early March 2014,” NATO said.
Meanwhile, the destroyer USS Donald Cook has entered the Black Sea on a mission to demonstrate U.S. commitment to its allies, Navy spokesman Lt. Shawn P. Eklund said Friday.
Russia has called the U.S. military move part of a systemic NATO buildup in the Black Sea.
Russia has no intention of annexing the southeastern regions of Ukraine, Foreign Minister Sergey Lavrov said Friday in a televised interview on Russian state television, the official ITAR-Tass news agency reported.
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