Blasts have sounded in Kharkov, the Ukrainian Strana media outlet reported, TASS reports.
It has not provided any additional details.
According to the official air raid alert resource, an air raid alarm was declared in central, southern and eastern Ukraine. Sirens sounded in Kiev, the Dnepropetrovsk, Kiev, Nikolayev, Odessa, Poltava, Kharkov, Cherkassy and Chernigov regions, as well as in the Kiev-controlled parts of the Zaporozhye and Kherson regions.