A U.N. aviation organization has sent a letter to North Korea to warn the communist regime over its recent ballistic missile launches that were conducted without prior notice, a Seoul government source said Tuesday.

"(I) understand the International Civil Aviation Organization

(ICAO) has sent a warning letter to the North under the name of its council chairman," the source said, declining to be named.

The letter appears to be intended to highlight that under the Convention on International Aviation, the North should file a notice with relevant aviation authorities to alert aircraft pilots of potential hazards should it want to launch any missiles. 

On Friday, the North fired two mid-range ballistic missiles in an angry response to the ongoing South Korea-U.S. military drills and the recent adoption of the U.N. Security Council resolution to punish the North for its latest nuclear test and rocket launch.

Last week, Seoul expressed its concern to the ICAO and the International Maritime Organization (IMO) that the North's launches of ballistic missiles without notice pose a "grave" threat to the safety of civilian aircraft and vessels.

Another Seoul government source said that the IMO would likely take a similar step to warn Pyongyang against any unreported missile launches. (Yonhap)