Romania's "aerial surveillance system" identified "groups of drones launched by the Russian Federation that attacked Ukrainian ports on the Danube," the ministry said. "During the mission, there were no penetrations of aircraft in the national airspace."

The incident highlights the continuing volatility near NATO's eastern border as Russia intensifies aerial attacks on Ukraine.

Russia launched a "massive drone strike" on the southern Ukrainian region of Odesa, injuring one person and causing a large fire at a fuel and energy facility, Ukraine's State Emergency Service said on Wednesday.