Russia will be "judged by its actions" after announcing a troop pullback from Ukraine's borders, British Defence Minister Ben Wallace said Wednesday.

"What we haven't seen is evidence of withdrawal that has been claimed by the Kremlin," Wallace told Sky News.

"In fact, we've seen continued build-up of things like field hospitals, and strategic weapons systems such as Iskander missiles deployed," he said, adding Britain "will judge them on their actions."

"Until we see a proper de-escalation, I think we should all be cautious about the direction of travel from the Kremlin."

Russia on Wednesday said military drills in Moscow-annexed Crimea had ended and that soldiers were returning to their garrisons, a day after it announced a first troop pullback from Ukraine's borders.

The statement said tanks, infantry vehicles and artillery were leaving Crimea by rail. 

But Wallace said there was intelligences that more than 100 battalion tactical groups were still ready for action. 

"They haven't taken the foot off the gas. If you wanted to inflict intimidation on Ukraine, that deployment is doing exactly that," he told Sky.

"That's why we need to see clear de-escalation by the removal of troops."

Wallace will meet with fellow NATO defence ministers in Brussels on Wednesday as part of diplomatic efforts to avert war.

He will hold talks with NATO Secretary General Jens Stoltenberg and US Defence Secretary Lloyd Austin.