U.S. fighter jets scrambled Wednesday to intercept four Russian warplanes off the coast of Alaska, the North American Aerospace Defense Command (NORAD) said Thursday.

NORAD said in a statement it detected and tracked four Russian military jets — two Tu-95s and two Su-35s — on Wednesday operating in the Alaskan Air Defense Identification Zone (ADIZ), a defined stretch of international airspace that begins where sovereign airspace ends. Identification of all aircraft in the zone is required.

NORAD responded with four F-16 fighter jets, an E-3 surveillance plane and four KC-135 refueling aircraft “to positively identify and intercept in the Alaskan ADIZ.”

The Russian military jets did not enter American or Canadian sovereign airspace, NORAD said, adding the “Russian activity in the Alaskan ADIZ occurs regularly and is not seen as a threat.”

“NORAD remains ready to employ a number of response options in defense of North America.”

The latest incident comes as NATO countries are on high alert after recent Russian incursions into their airspace.

European Commission President Ursula von der Leyen said Wednesday that shooting down Russian fighter planes entering NATO airspace was “on the table.” 

“My opinion is we have to defend every square centimeter [of] territory, and that means if there’s an intrusion in the airspace, after warning, after being very clear, of course, the option of shooting down a fighter jet that is intruding our airspace is on the table,” von der Leyen said during an appearance on CNN. 

President Trump said Tuesday during his meeting with Ukrainian President Volodymyr Zelensky at the United Nations General Assembly that NATO countries should shoot down Russian jets that enter its airspace.