Polish police, border guards and military personnel launched a large-scale operation along the border with Russia’s Kaliningrad exclave after intelligence services warned that armed individuals might enter Polish territory, Prime Minister Donald Tusk said.

Tusk said he was informed shortly after midnight about what he described as concerning activity near the border. People carrying flashlights were reportedly seen in the area. He said the security forces acted quickly and prevented possible provocations, while cautioning that it would not be possible to confirm their nature with certainty.

According to Tusk, intelligence agencies had previously warned that hostile services might plan provocations at the border in early November. He said NATO Supreme Allied Commander Alexus Grynkewich had also confirmed the information.

Poland and the Kaliningrad exclave share a 232-kilometer border. Tensions have risen in the area: in late September, Poland’s army said a military helicopter from Kaliningrad briefly entered Polish airspace and accused Russia of testing the readiness of Polish air defenses.

Sources: Der Spiegel.