Library image of Russian paratroopers jumping from an Ilyushin Il-76 plane. (Image: PA).
NATO member Estonia has said a Russian military aircraft entered its airspace near the Baltic Sea island of Vaindloo.
It is the second such alleged incident this week and the third in a month.
The IL-76 plane spent less than one minute in the country's airspace on Thursday afternoon, the Estonian military said.
Estonia said the plane's transponder was switched on but the crew did not present a flight plan and had no radio contact with Estonia's air navigation service.
The foreign ministry summoned Russia's ambassador and handed him a note.
Estonia has reported four alleged airspace violations by Russian planes this year.
The military said an almost identical violation took place at the same location on Tuesday.
Estonian media said the IL-96 passenger plane in that incident allegedly belonged to Russia's presidential administration.