The Ukrainian Security Service and Antiterrorist Center are beginning an antiterrorist operation in the country, Ukrainian Security Service Head Oleksandr Yakymenko said in a statement released on Wednesday.

"The Ukrainian Security Service and Antiterrorist Center decided today to start holding an antiterrorist operation in Ukraine … I have already informed the president of the decision regarding holding the antiterrorist operation," the document said.

The events of the past day showed "growing escalation of forceful resistance and mass use of arms by extremist-minded groups," Yakymenko said.

"In many regions of the country local authorities, structures of the Interior Ministry, Security Service, prosecutor's office, military units and storage facilities with ammunition are being seized. Court offices are burning and vandals are destroying private apartments and killing civilians," the statement said.

In the past 24 hours alone over 1,500 units of firearms and 100,000 pieces of ammunition ended up in criminal hands, Yakymenko said.