Polish fighter jets intercepted a Russian plane carrying out a reconnaissance mission in international airspace over the Baltic Sea, Reuters reports.
The Polish military said it had no flight plan and its transponder was off.
NATO's eastern flank has been on high alert for potential violations of its airspace since September, when three Russian military planes invaded the skies over Estonia for 12 minutes. The incident occurred just days after more than 20 Russian drones entered Polish airspace.
"Polish fighter jets intercepted an Il-20 aircraft carrying out a reconnaissance mission in international airspace, without a filed flight plan and with its transponder turned off. The plane did not violate Polish airspace," the Polish Armed Forces Operational Command said.
Polish Army Operational Command spokesman Jacek Gorishevsky said the incident showed that Poland "is vigilant to ensure that our airspace is not violated".
Last week, Alexis Grinkiewicz, a U.S. Air Force general and NATO's Supreme Allied Commander Europe, noted that Russia appeared to have been deterred by NATO's firm response last month to incursions into Polish and Estonian airspace, but Moscow is expected to continue testing the limits.