BRUSSELS - NATO on Wednesday defended the number of military exercises it has staged as a response to "growing Russian aggression" and refuted suggestions that they were helping make war in Europe more likely.

The alliance was reacting to a warning from a London-based think tank about the risks from a sharp increase in Russian and NATO war games since the conflict between the Ukrainian government and pro-Russian separatists flared up in April last year.

"NATO military exercises are not, as the reports suggest, making war in Europe more likely," NATO spokeswoman Carmen Romero said after the European Leadership Network (ELN) published its assessment.

"They are intended precisely to have the opposite effect: to enhance security and stability in Europe in response to growing Russian aggression," Romero said in a statement.

"All NATO military activities are proportionate, defensive, and fully in line with our international commitments," she added.

The ELN report was titled: "Preparing for the Worst: Are Russian and NATO Military Exercises Making War in Europe more Likely?"

The ELN report authors said the nature and scale of the exercises contradicted claims from both sides that they targeted hypothetical opponents.

"Russia is preparing for a conflict with NATO, and NATO is preparing for a possible confrontation with Russia," ELN said.(AFP)