A Polish military spokesman says a Polish amphibian transporter sank after a NATO landing exercise in the Baltic Sea but both crew members have been rescued safely.

The amphibian sank Wednesday 150 meters (yards) off the beach in Ustka, in northern Poland, as it was returning to its transport ship.

Maj. Michal Romaniuk told The Associated Press that a nearby observers' ship took both crew members on board. He said a commission will look into the cause of the sinking.

The landing exercise of 700 troops was part of the massive BALTOPS 2015 maneuvers that NATO is holding on its eastern flank to reassure eastern members in the face of a resurgent Russia.