"Russia needs to stop supporting the militants and withdraw its forces and military equipment from Ukrainian territory," Stoltenberg said after a meeting of NATO defence ministers with their Ukrainian counterpart in Brussels.
He said the US-led alliance will continue to stand by the government in Kiev and would never recognise Russia's "illegal and illegitimate annexation of Crimea".
"In response to Russia's actions, NATO has stepped up its support for Ukraine. Our level of political and practical engagement since 2014 is unprecedented," he said.
