The U.S. State Department has sharply rebuked North Korea for accusing U.S. spy aircraft of violating its exclusive economic zone(EEZ) and threatening to shoot down such planes.

A department spokesperson issued the position on Tuesday in response to an inquiry by the South Korean media regarding the North’s claim.

The spokesperson said that the North’s recent statements that U.S. aircraft flew into its EEZ illegally are “unfounded” as high seas freedoms of navigation and overflight apply in such areas.

The spokesperson then criticized the North’s threat to shoot down flights in the international airspace as "reckless" and "irresponsible."

The U.S. rhetoric appears to have become stronger since the previous day, when department spokesperson Matthew Miller urged North Korea to refrain from escalatory actions and to engage in diplomacy after Pyongyang made the accusation.

Sabrina Singh, deputy spokesperson for the U.S. Department of Defense, said on Monday that the U.S. always operates responsibly, safely and in accordance with international law, dismissing the North Korean accusation as groundless.