Ukraine's allies have warned against the European Union reopening Russian gas pipelines as part of a prospective peace settlement.

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.

North Korean soldiers had been missing from combat, fueling speculation they were pulled back after taking heavy losses.