Russian missile attacks on state-owned natural gas assets in Ukraine have forced the country to buy expensive replacement fuel from the European Union, according to people with knowledge of the matter.

Though North Korean ballistic missiles account for only a small portion of Russia's missile strikes they carry a large warhead of up to one tonne and have a range of up to 800 km, the military source said. The Iskander-M, an equivalent Russian missile, carries a smaller payload and has a shorter range of 500 km.

A Russian strike killed five civilians and wounded 55 on Tuesday in the town of Izium in Ukraine's northeastern Kharkiv region, partially destroying the city council building, officials said.