Two simultaneous bomb blasts occurred in eastern Ukraine, in the town of Makiyivka, early on January 20 2011, without any casualties, media reports said.
The blasts occurred at 6am local time, the first near the building of a local coal company and the other at the city's market.
An unidentified group threatened several more blasts in the Ukrainian town of Makeyevka unless they are paid "a large amount of money", deputy interior minister Vasyl Farynnyk said.
Last October, three small bombs exploded near the government buildings in another Ukrainian city of Kirovograd, just prior to the planned visit by president Viktor Yanukovich.
The blasts shattered several windows in one of the buildings but caused no injuries. Police called the incident an act of hooliganism.