President Joe Biden called an “emergency” meeting of G7 and NATO leaders in Indonesia Wednesday morning for consultations after NATO-ally Poland said a “Russian-made” missile killed two people in the eastern part of its country near the Ukraine border.

Biden, who was awakened overnight by staff with the news of the missile explosion, called Polish President Andrzej Duda early Wednesday to express his “deep condolences” for the loss of life. The U.S. president promised “full U.S support for and assistance with Poland’s investigation,” and “reaffirmed the United States’ ironclad commitment to NATO.”

A statement from the Polish Foreign Ministry identified the missile as being made in Russia. But Poland’s president, Duda, was more cautious about its origin, saying that officials did not know for sure who fired it or where it was made. He said it was “most probably” Russian-made, but that is being still verified. If confirmed, it would be the first time since the invasion of Ukraine that a Russian weapon came down on a NATO country.

The foundation of the NATO alliance is the principle that an attack against one member is an attack on them all.