Polish jets intercepted a Russian reconnaissance plane over the Baltic Sea, which was flying close to its airspace, the NATO member country's army said on Thursday.

Countries on NATO's eastern flank have been on high alert for potential airspace incursions since September when three Russian military jets violated Estonia's airspace for 12 minutes just days after more than 20 Russian drones had entered Polish airspace.

"This morning, over the international waters of the Baltic Sea, Polish fighter jets intercepted, visually identified, and escorted from their area of ​​responsibility a Russian reconnaissance aircraft flying near the borders of Polish airspace," the army said.

It also said that at night, objects were observed entering Polish airspace from the direction of Belarus.

"After detailed analysis, it was determined that these were most likely smuggling balloons, moving in accordance with the wind direction and speed," the army said. It added that part of the airspace over northeast Poland's Podlaskie region, which borders Belarus, was temporarily closed to civilian traffic to ensure security.

-Anna Koper/Reuters