Donetsk remains eerily calm while tensions continue in eastern Ukraine

The atmosphere in central Donetsk, the nerve center of Ukraine's industrial heartland, was largely calm on Wednesday.

Protesters — mostly pensioners and youngsters — milled about near the barricades that block off the occupied regional administration building, while tacky, patriotic songs in Russian blared from a makeshift stage near the entrance.

The walls of tires, wood and barbed wire were festooned with crude admonishments of both the authorities in Kyiv and the United States, who many here accuse of sponsoring the "coup" that toppled President Viktor Yanukovych.

They're guarded mostly by masked, disheveled men occasionally armed with a club or sporting a bulletproof vest. Many appear tired, while others physically worn. They're a far cry from the armed rebels who've seized official buildings in provincial eastern Ukraine.

The most active supporters here appear to be the pensioners, who espouse a near-universal nostalgia for the Soviet Union and have been the most susceptible to the Russian state media's heavy-handed propaganda campaign.

On Wednesday afternoon, they complained to this GlobalPost reporter about what they alleged was US meddling in Ukrainian affairs. They were convinced, among other things, that the snipers who fired on protesters in Kyiv in late February were Americans.

Elsewhere in Ukraine, the situation seemed more tense after US Vice President Joe Biden's visit. Militants in eastern Ukraine confirmed they had detained an American reporter who works for Vice magazine.

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"There's nothing wrong with [Simon] Ostrovsky," the self-declared mayor of Slovyansk, Vyacheslav Ponomaryov, said, according to Reuters. "He is with us, he is feeling well and in a clean place. He is not a hostage but our guest. We only gave him a place of residence."

The European Union on Wednesday called on Russia to use its leverage with pro-Russian separatists to ensure the kidnappings and killings in eastern Ukraine end. The statement came after the reported death of a local politician.

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International monitors sanctioned by the Organization for Security and Cooperation in Europe have gone into eastern Ukraine to persuade the armed separatists to lay down their weapons, according to Reuters. The 100 monitors are only armed with copies of the deal that was crafted between the United States, Russia, Ukraine and Europe on April 17.

Meanwhile, Russian Foreign Minister Sergei Lavrov accused the United States of being behind the political unrest and warned that Russia would respond if its interests in the region came under attack.

The authorities in Ukraine's capital, Kyiv, earlier announced that they would resume a security operation against the armed separatists in the eastern parts of the country, increasing fears of a crackdown.

Reuters contributed to this report.