WASHINGTON - US President Donald Trump on Thursday said that the alleged Russian drone incursion into Poland's airspace "could have been a mistake", while expressing frustration with the incident.

"It could have been a mistake, but regardless, I'm not happy about anything having to do with that whole situation," Trump told reporters.

"I don't like it," he said. "Hopefully it's going to come to an end."

In his first response to the incident, Trump wrote on Truth Social platform on Wednesday: "What's with Russia violating Poland's airspace with drones? Here we go!"

His remarks so far stand in contrast to the strong statements from European leaders, some of whom accused Russia of carrying out a deliberate drone incursion to test the readiness of the North Atlantic Treaty Organization (NATO).

Russia has rejected the accusation made by Poland, the EU, and NATO that it launched the drones. The Russian Defense Ministry said that none of its strike targets were in Poland, while Kremlin spokesman Dmitry Peskov said the EU and NATO "accuse Russia of provocations on a daily basis" without evidence.

The Polish military shot down drones over Poland after its airspace was repeatedly violated overnight from Tuesday to Wednesday, according to a statement from the Polish Armed Forces Operational Command.

ALSO READ: Russia calls on Poland to reconsider closing border with Belarus

Polish Prime Minister Donald Tusk had invoked Article 4 of the North Atlantic Treaty, seeking consultations with NATO allies over a threat to national security.

NATO Secretary-General Mark Rutte said on Wednesday that NATO will continue to closely monitor the situation in the east, with its air defense systems kept on standby.