BRUSSELS: NATO could deploy additional combat units in eastern Europe in response to Russia's military build-up on Ukraine's border, NATO Secretary-General Jens Stoltenberg said on Monday.

"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.

NATO beefs up eastern flank, Russia denounces Western 'hysteria'

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