Warsaw: NATO Secretary-General Jens Stoltenberg has criticised Russia during a visit to Poland, repeating his call for Moscow to accept responsibility for the 2014 downing of Malaysia Airlines Flight MH17 over Ukraine

"I agree with the Dutch government, which calls on Russia to take responsibility for the crash," Stoltenberg said, describing the incident which killed all 298 passengers, including 38 Australians, as a "direct consequence" of Russian aggression towards Ukraine.

The Netherlands and Australia accused Russia of downing flight MH17 after a team of international investigators found that the Buk anti-aircraft system used to bring down the jet belonged to Russia.

Stoltenberg, citing Russian interference in elections, cyber attacks, and their use of military force against neighbouring countries, went on to say that this "more assertive" Russia is one of the biggest security challenges for NATO states.