A US surveillance aircraft has flown over South Korea, an aviation tracker said Wednesday, on an apparent mission to monitor North Korea just days after the communist nation fired what are believed to be two short-range ballistic missiles.

The US Navy's EP-3E was spotted in skies above South Korea on Tuesday, Aircraft Spots tweeted.

The operation came two days after North Korea fired two projectiles from the eastern coastal city of Wonsan toward the East Sea, marking the fourth major weapons test the North has conducted this year.

The United States flew the same type of plane over the peninsula Sunday, the same day the North fired the two projectiles.

Amid stalled denuclearization talks with the US since the no-deal Hanoi summit in February last year, the North has called for boosting self-defense capabilities.

On Monday, North Korea lashed out at US Secretary of State Mike Pompeo for seeking continued international pressure against Pyongyang, threatening to "hurt" the US and go its "own way." (Yonhap)