Polish President Andrzej Duda said on social media that he was "deeply saddened by the tragic aviation accident at Ronald Reagan Washington National Airport," which left no survivors, according to media reports.
"My thoughts and prayers are with the families and loved ones of the victims," Duda added.
"On behalf of the Polish people, I extend my sincere condolences to President Donald Trump and the American nation," he also wrote.
Polish Prime Minister Donald Tusk offered his "deepest condolences on the loss of so many lives in the Washington plane crash."
Scores of people were feared dead after the jet and the helicopter crashed into the frigid river near Reagan Washington National Airport, the Reuters news agency reported.
Sixty-four people were onboard the American Airlines plane, and the Black Hawk helicopter had three soldiers on board for a training flight, according to officials.
"Today we are all with the American people in this tragic moment," Tusk said in a post on the X social media platform.
The Polish foreign ministry said it was "shocked by the tragic crash of a passenger plane and helicopter near Washington's Reagan National Airport."
It added: "At this difficult time, we extend our deepest sympathies to the families of the victims and to the entire 🇺🇸 nation."
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Source: IAR, PAP, Reuters