European Commission President Ursula von der Leyen and Polish Prime Minister Donald Tusk visited the Polish-Belarusian border on Sunday in a show of support for Poland and other states on the EU's eastern flank.

At a border post near Krynki, the two leaders were briefed by Polish border guards and military command staff, the services involved in protecting the frontier.

Von der Leyen assured Tusk and the Polish people of "Europe’s full solidarity with Poland as a frontline state," and referred to Russian President Vladimir Putin as a "predator."

"We have to keep the sense of urgency because we know that Putin has not changed and will not change,” she said.

"We know by experience that he can only be kept in check through strong deterrence."

She vowed that the EU would also financially support increased border defenses, stressing that Poland's border is the frontline for all Europe.

Von der Leyen also vowed to continue supporting Ukraine in defending itself against Russian aggression.