Russia is not giving up on its offensive in Ukraine but will try to refocus on completely taking the Donbas region in the coming weeks, NATO Secretary-General Jens Stoltenberg said on Tuesday.

"We now see a significant movement of (Russian) troops away from Kyiv to regroup, re-arm and re-supply and shift their focus to the east," Stoltenberg told a news conference.

"In the coming weeks, we expect a further Russian push in eastern and southern Ukraine to try to take the entire Donbas and to create a land bridge to occupied Crimea," he said before Wednesday's meeting of NATO foreign ministers.