Poland's president says the downing of a passenger plane in rebel-controlled eastern Ukraine reinforces the need for NATO to strengthen its defenses on its eastern flank.

Bronislaw Komorowski described the shooting down of the plane as a terrorist act and said it should mobilize central and eastern European countries to find ways to enhance their defenses. He encouraged the region's leaders to increase their defense budgets.

Komorowski spoke to reporters Tuesday on the sideline of a meeting with the presidents of eight other countries in central and eastern Europe, all ex-communist countries now in NATO and the European Union. The leaders met ahead of a NATO summit in September.

The region has been divided over how to respond to Russian aggression in Ukraine, which is not a member of NATO.