NATO may deploy additional combat units in Eastern Europe in response to "a build-up of Russian military power on the border with Ukraine," NATO Secretary-General Jens Stoltenberg said, Reuters reported.

"We are considering to further enhance our presence in the eastern part of the alliance, this could include the deployment of additional NATO battlegroups," Stoltenberg told reporters in Brussels.

So far, NATO has deployed about 4,000 troops in multinational battalions in Estonia, Lithuania, Latvia and Poland, supported by tanks, air defenses and intelligence and surveillance units.