KYIV, Ukraine -- The Ukrainian military is sharing with European countries its expertise in fighting Russian drones, sending a mission to Denmark for joint exercises, Ukraine President Volodymyr Zelenskyy said Tuesday. “Our military has begun deploying a mission in Denmark to disseminate Ukrainian experience in drone defense," Zelenskyy said.

Drone overflights again caused disruptions at Danish airports on Wednesday night, officials said, in the latest instance of unexplained drone sightings.

Denmark is stepping up its drone defenses before European leaders meet in Copenhagen this week, as a new suspected drone intrusion temporarily shut airspace and intensified security concerns.

A drone swarm that flew over Germany's Schleswig-Holstein state deliberately surveyed the NATO ally's critical infrastructure, including a power plant and a naval facility, according to a report by Der Spiegel, which cited an internal government memo.

Denmark bans drone flights while ‘brutal’ attack on Kyiv kills four - Nato member says it is in 'difficult security situation' amid unexplained drone activity ahead of EU meeting

A NATO spokesperson said they would not provide details on which countries were contributing the extra assets. The new assets will enhance NATO's "Baltic Sentry" mission, launched in January in response to a string of incidents in which power cables, telecom links and gas pipelines on the Baltic Sea bottom have been damaged.

The Russian invasion of Ukraine should have already led to better drone defenses in Europe. Now, the recent incidents in Poland, Denmark and other countries continue to be a wake-up call.

The EU is under pressure to boost defence after Russian air space incursions and after drones targeted Danish airports.