POLISH and allied aircraft were deployed in a “preventive” operation in Poland’s airspace on Saturday over the threat of drone strikes in neighbouring areas of Ukraine, with the airport in the eastern Polish city of Lublin also closed, authorities said.

The alert, which lasted around two hours, came after multiple Russian drones crossed into Poland on Wednesday, prompting Nato to send fighter jets to shoot them down and underlining long-held concerns about the expansion of Russia’s three-year-plus war in Ukraine.

The Polish military’s operational command posted said on Saturday afternoon that ground-based air defence and reconnaissance systems were on high alert.

It stressed that “these actions are preventive in nature,” and were aimed at securing Poland’s airspace and protecting the country’s citizens.

It cited a threat of drone strikes in regions of Ukraine bordering Poland, but didn’t give further details.

Prime Minister Donald Tusk also posted that “preventive air operations” had begun in Polish airspace because of the threat posed by Russian drones operating over nearby areas of Ukraine.

The Polish Air Navigation Services Agency said that Lublin airport was closed to air traffic “due to military aviation activities,” and the government security centre warned of a threat of air attack for several border counties in the region.

Later on Saturday, the military’s operational command wrote on social media that the operation “has been completed” and that ground-based defence and reconnaissance systems had returned to normal.

Russia has said it didn’t target Poland on Wednesday, and Moscow’s ally, Belarus, said that the drones went astray because they were jammed. But European leaders have claimed that the incursions were a deliberate provocation by Russia.

Polish aircraft have been scrambled repeatedly in recent months to patrol the country’s airspace in connection with Russian air strikes in Ukraine, but those strikes have usually occurred overnight or in the early morning.

Separately, Romania said it deployed two F-16 jets to intercept a drone that briefly entered its airspace on Saturday afternoon.

“The drone did not fly over inhabited areas and did not represent an imminent danger to the security of the population,” the Nato member’s defence ministry said in a statement.