NATO must enact a "robust coordinated" response to incidents in which Russian missiles or drones fired at Ukraine enter the alliance's airspace, Romanian Defence Minister Angel Tilvar said on Wednesday.

States on NATO's eastern flank, whose defence ministers met in Bucharest on Wednesday, have repeatedly said Russia's activities in the Black Sea region and beyond were a source of deep concern.

Earlier this month, NATO states Romania and Latvia saw Russian drones crash after breaching their airspace, prompting official calls for measures to act jointly to counter Russia air incursions.

Last week Ukraine accused Russia of using strategic bombers to strike a civilian grain vessel in a missile attack in Black Sea waters near Romania, further escalating tensions between Moscow and the military alliance.

"B9 states are profoundly concerned about the repeated incursions of Russia's drones and missiles in NATO air space, in Poland, Romania, Latvia, as well as escalating tensions along NATO's eastern flank," Tilvar told reporters, referring to the regional grouping of NATO members.

"That is why a robust, coordinated response on an allied level is needed as well as enforcing the rotational air defence and integrated anti-missile model as soon as possible."

Polish deputy defense minister Pawel Zalewski said a meeting of NATO defence ministers in October will need to address destroying drones entering allied air space.

"We have confirmed hybrid attacks on allies, as well as the participation of Belarus in Russia's actions," Zalewski added.

Romania shares a 650-km (400-mile) border with Ukraine and has had Russian drone fragments stray into its territory repeatedly over the past year. Romanian territory lies close to Ukrainian Danube River ports, frequent Russian targets3