Crowds of pro-Russian demonstrators stormed government buildings Sunday in several major cities in eastern Ukraine, where secessionist sentiment has sparked frequent protests since Ukraine's Russia-friendly president was ousted in February.
In Donetsk, 50 miles west of the Russian border, a large group of people, including many in masks carrying sticks and stones, surged into the provincial government building and smashed windows.
A gathering of several hundred, many of them waving Russian flags, then listened to speeches delivered from a balcony emblazoned with a banner reading "Donetsk Republic." Activists in the building said they want to see a referendum for the Donetsk province to join Russia.
An AP photographer reported seeing people bringing car tires to be used as barricades against any presumed attempt by authorities to retake the building.
Eastern Ukraine was the heartland of support for Viktor Yanukovych, the president who fled to Russia in February after months of protests. About half of the region's residents are ethnic Russians, many of whom believe Ukraine's acting authorities are Ukrainian nationalists who will oppress Russians.
Ukraine's interim authorities deny they are infringing the rights of the ethnic Russian population and accuse Moscow of trying to sow instability. Russia has moved large contingents of troops to areas near the Ukrainian border, and speculation is strong that unrest in eastern Ukraine could be used as a pretext for a Russian incursion.
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Since Crimea held a referendum to secede and then was annexed by Russia in March, calls for similar referenda in Ukraine's east have emerged.
President Oleksandr Turchinov's office said in a statement he had canceled a planned visit to Lithuania this week to take personal charge over the situation in eastern Ukraine.
In Luhansk, to the northeast from Donetsk, hundreds of people surrounded the local headquarters of the security service and later scaled the facade to plant a Russian flag on the roof. Ukrainian media reported that demonstrators pelted the building with eggs, and then stones, a smoke grenade and finally a firebomb. The flames were reportedly quickly extinguished.