NATO has instructed its commanders to work out the details of deploying combat groups on the alliance's southeastern flank in response to Russia's military build-up near Ukraine's borders, Secretary-General Jens Stoltenberg said, Reuters reports.

"Ministers decided to develop options to further strengthen NATO's deterrence and defence, including to consider establishing new NATO battlegroups in central and eastern and southeastern Europe," Stoltenberg told reporters at a two-day meeting of the alliance's defence ministers in Brussels.

"Our military commanders will now work on the details and report back within weeks," he added.