NATO launched a large-scale exercise, the "Steadfast Javelin 1" in Estonia on Friday, in order to test the allied forces' capability and maintain NATO's readiness and combat effectiveness, a NATO statement said.

Around 6,000 troops from Belgium, Denmark, Estonia, France, Latvia, Lithuania, Poland, the United Kingdom and the United States are participating in the exercise which will run until 23 May.

"The exercise reflects NATO's strong commitment to collective defence in the Baltic region," said Commander Allied Joint Force Command Brunssum, General Hans-Lothar Domrose.

The exercise is based on a fictitious scenario and involves participating allied forces repelling an attack on Estonia. Participating units include infantry and reconnaissance forces, engineers, fighter jets as well as anti-aircraft teams and a cyber security team.

The North Atlantic Council on 16 April agreed on a package of extra military measures to reinforce the alliance's collective defence in wake of the crisis in Ukraine, which include enhanced exercises, updated defence plans and appropriate deployments, according to the statement.