1/12An elderly couple dances as local citizens gather to observe May Day in Slovyansk, May 1, 2014.
Ukraine's acting president says its military is "on full combat alert" against a possible invasion by Russian troops massed on the border.
2/12Participants hold a Soviet flag near a statue of Soviet leader Vladimir Lenin during an International Worker's Day, or Labor Day, parade in the town of Slovyansk, May 1, 2014.
Ukraine's acting president says its military is "on full combat alert" against a possible invasion by Russian troops massed on the border.
3/12Participants shout slogans and wave Russian flags during an International Worker's Day parade in Donetsk, May 1, 2014.
Ukraine's acting president says its military is "on full combat alert" against a possible invasion by Russian troops massed on the border.
4/12Local citizens march to observe May Day in the central square in Slovyansk, May 1, 2014.
Ukraine's acting president says its military is "on full combat alert" against a possible invasion by Russian troops massed on the border.
5/12A pro-Russian armed man waves to participants of an International Worker's Day parade in the town of Slovyansk, May 1, 2014.
Ukraine's acting president says its military is "on full combat alert" against a possible invasion by Russian troops massed on the border.
6/12Ukrainian government troops guard a checkpoint near the village of Dolina, 30 kilometers from Slovyansk, May 1, 2014.
Ukraine's acting president says its military is "on full combat alert" against a possible invasion by Russian troops massed on the border.
7/12Ukraine's acting president Oleksandr Turchynov chairs a meeting at the presidential administration stating that Ukraine's police and security forces are "helpless" to quell unrest in two eastern regions bordering Russia, Kyiv, April 30, 2014.
Ukraine's acting president says its military is "on full combat alert" against a possible invasion by Russian troops massed on the border.
8/12Pro-Russian activists gather at a barricade outside the regional government headquarters in Luhansk, April 30, 2014.
Ukraine's acting president says its military is "on full combat alert" against a possible invasion by Russian troops massed on the border.
9/12Members of self-defense units of the Euromaidan movement (front) attack members and supporters of Ukrainian far-right radical groups (back) to prevent them from taking part in a torchlight procession, Kyiv, April 29, 2014.
Ukraine's acting president says its military is "on full combat alert" against a possible invasion by Russian troops massed on the border.
10/12A pro-Russian activist waves a Donbas Republic flag over a crowd celebrating the capture of an administration building in the center of Luhansk, April 29, 2014.
Ukraine's acting president says its military is "on full combat alert" against a possible invasion by Russian troops massed on the border.
11/12Pro-Russian masked and armed militants check the bus passengers' luggage, Slovyansk, Wednesday, April 30, 2014.
Ukraine's acting president says its military is "on full combat alert" against a possible invasion by Russian troops massed on the border.
12/12Pro-Russian masked and armed militants guard barricades near Slovyansk, April 30, 2014.
Ukraine's acting president says its military is "on full combat alert" against a possible invasion by Russian troops massed on the border.
Russian Foreign Minister Sergei Lavrov has called for talks between Kyiv and pro-Russian separatists in southeastern Ukraine.
"Russia believes that this dialogue between the authorities in Kyiv and their opponents could be established, or launched in the framework of the Organization for Security and Cooperation in Europe. We hope that our partners, our Western colleagues allow Ukrainians to establish this dialogue without major impediment.''
The prime minister spoke during a visit to Peru.
In eastern Ukraine, local authorities said Wednesday pro-Russian gunmen seized control of a city council building in Horlivka, a city of 290,000 residents north of the industrial hub of Donetsk. Separatists now control about a dozen cities in Ukraine's industrial east, including Donetsk, where rebels have set a referendum on secession for May 11.
A similar vote last month led to Russia's annexation of the Crimean peninsula.
Ukraine's interim president Oleksandr Turchynov has said his government is "helpless" to quell the growing pro-Russian separatist movement in two eastern regions and cannot control its own troops.
Meanwhile, the International Monetary Fund slashed Russia's growth forecast for 2014 from 1.3 percent to 0.2 percent. The IMF says its decision took into account "the significant level of uncertainty" related to geopolitical tensions and sanctions against Russia for its role in the Ukraine crisis.
