Germany, France, Italy, Poland and the United Kingdom also underscored their "unwavering support" for Ukraine in its war with Russia, and their commitment to rebuilding their own militaries.

"We will intensify our cooperation in countering hybrid threats against allies, including addressing the challenges posed by drones, cyberattacks, and disinformation," the allies said in a joint statement.

This will include exploring defence measures "such as drone defence systems" as well as "enhancing information sharing among European allies", they said.

European countries have repeatedly accused Russia of conducting "hybrid" warfare -- a largely unconventional warfare that can involve sabotage, disinformation campaigns and other disruptive attacks.

Several drone sightings have been reported at airports and sensitive military sites across Europe in recent months, with leaders pointing the finger at Moscow.

Airports in Belgium, Denmark, Germany, Norway and Poland have been among those affected.

Speaking after the meeting, German Defence Minister Boris Pistorius said such actions were designed to "divert attention from (Russia's) own problems... while at the same time attempting to unsettle and frighten our societies".

The five defence ministers, who were also joined by European Union foreign policy chief Kaja Kallas, also vowed to keep up their support for Ukraine as it fends off Russia's invasion.

"Our unwavering support for Ukraine will continue to be a central pillar of our work," they said, pledging "to maximise support to Ukraine through military aid".

They also pledged to ramp up industrial cooperation with Ukraine as well as "integrating the Ukrainian defence industry into European initiatives and value chains".

The ministers also promised to focus on meeting their NATO military capability targets and ramping up their defence industries.

"Russian aggression is growing. The war in Ukraine continues to rage. The US has rightly challenged European nations to do more and to spend more on defence," said Britain's Defence Minister John Healey.

"Make no mistake -- we are in a new era of threat and this demands a new era for defence," he said.