Simferopol, Crimea (CNN) -- A deadline Ukraine's acting President gave Crimea's separatist leaders to release hostages came and went without apparent incident Wednesday, after pro-Russian activists stormed the former Soviet state's navy headquarters in the region. Amid signs the uneasy standoff between pro-Russian and Ukrainian forces could ignite into bloody conflict -- a day after Moscow claimed Crimea as its own -- almost 300 armed pro-Russian supporters took over the naval base in Sevastopol, said Marina Kanalyuk, assistant to the commander of Ukraine's navy fleet. "They are everywhere here, they surround us, they threaten us," she said, adding that she was sure that Russian security forces were involved.
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NEW: "Business as usual is not an option," says NATO secretary general
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NEW: He warns of the organization's fear that Russia may move into eastern Ukraine
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Ukraine says prepared to evacuate military personnel and family members from Crimea
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On visit to Baltic states, U.S. Vice President Joe Biden slams Russian "aggression"
ET) deadline for @placeholder to release all hostages and stop all provocations, a statement on the presidential website said.
But the ballot questions offered no real option for any residents who wanted to remain part of @placeholder.
Members of the @placeholder parliament and the new Crimean legislature met Wednesday morning in Moscow to discuss the details of how the region will join Russia.