WARSAW, Poland (AP) — Poland's president has warned that Europe must learn lessons from World War II and must not tolerate any return to imperialist land grabs, an apparent reference to Russian aggression in Ukraine.

Andrzej Duda was speaking Thursday at a ceremony marking the 77th anniversary of the start of World War II. He made his remarks on the Westerplatte peninsula in Gdansk on Poland's Baltic coast, where some of the war's first shots were fired at 4.45 a.m. on Sept. 1, 1939. There, a Polish army outpost held out for a week against German naval and air attacks.

Duda said: "We cannot allow imperial ambitions and actions to return to Europe. ... We cannot shut our eyes when international laws are violated ... or when borders in Europe are moved by force."