Ukrainian counterattacks near the Russian border in Kharkiv leave Moscow "very worried," according to a senior Ukrainian official.
Russian forces, however, are strong enough for another attack in the area, the official said.
The missiles hit two areas of Sloviansk in eastern Ukraine, according to the city's mayor.
The city is a prime target for Russian forces trying to push south into the Donetsk region.
Ukraine will suspend some of the Russian gas exports to Europe that flow through pipelines through the country due to disruptions at key transit points, the gas transmission system operator said.
