The European Aviation Safety Agency says there was a significant increase last year in incidents involving civilian and military aircraft over the Baltic Sea and measures are needed to reduce risks.

NATO has complained that Russian military aircraft regularly fail to file flight plans or communicate with controllers, and fly with their transponders switched off.

An EASA report released Tuesday didn't explicitly mention Russia but referred to a significant increase in 2014 in "safety occurrences involving civil and non-cooperative military aircraft." It said that "the risk to civil aviation is high and this means that mitigating measures to reduce the risk to an acceptable level need to be taken."

It recommended that countries work to ensure that, when flying over the seas, "'due regard' for civil aircraft is always maintained."