North Korea's military said it had scrambled warplanes after a US reconnaissance aircraft intruded into its economic zone off its east coast, state news agency KCNA reported on Friday.
The incident, which occurred on Thursday, was "a dangerous military provocation" and North Korea was considering measures to deter future incursions, an unnamed spokesperson of the General Staff of the Korean People's Army said in the report.
The incident came ahead of a summit on Friday of the United States, South Korea and Japan. A South Korean lawmaker, citing that country's intelligence agency, said on Thursday that North Korea may launch an intercontinental ballistic missile or take other military action to protest the meeting.
President Joe Biden will meet at Camp David in Maryland with South Korean President Yoon Suk Yeol and Japanese Prime Minister Fumio Kishida, hoping to tighten ties between Seoul and Tokyo amid nuclear threats from North Korea and at a time when China's regional influence is growing.
South Korea and the United States are also due to begin 11 days of joint military drills on Monday.