Bucharest: Russian President Vladimir Putin wants "to use winter as a weapon of war" in his campaign in Ukraine, NATO chief Jens Stoltenberg said Tuesday in Bucharest ahead of a meeting of the alliance's foreign ministers.

"We have to be prepared for more refugees crossing into the rest of Europe," as a result of Russia's "deliberate attack on critical services, heating, light, water, gas" in Ukraine, Stoltenberg said.