The United States said Wednesday it has expressed concern to the U.N. aviation safety agency about North Korea's recent launches of rockets and missiles without prior safety notifications, saying such firings show Pyongyang's disrespect for international rules.

State Department spokeswoman Jen Psaki said the U.S. joined other nations on July 8 in co-signing a letter to the president of the International Civil Aviation Organization about "serious threats" posed by the North's recent test shots.

"North Korea's decision to conduct these launches without prior notification threatens the safety of international aviation and demonstrates North Korea's disregard for the rules and regulations of the organization, and hence our effort to express our concern from the United States," she said at a regular press briefing.

North Korea has fired a number of missiles, rockets and artillery rounds off its east coast in recent weeks. But the communist regime carried out the launches without posting advance notifications aimed at ensuring that flights stay away from affected areas.

Psaki reiterated the U.S. is concerned about the North's recent launches.

"According to our information, North Korea launched two Scud-class short-range ballistic missiles from its southwest region on July 13th. Both missiles flew in a northeasterly direction and impacted the sea," she said. "This is yet another violation of multiple U.N. Security Council resolutions."

She said such provocative actions heighten tensions in the region and will not provide North Korea the prosperity and security it claims to seek.

Despite such repeated expressions of concern, however, the U.S. has not taken any action against the North. Asked whether the U.S. has any plan to raise the issue at the Security Council, Psaki only said it is the Security Council itself that has the lead on deciding next steps.

"I can check on that and see if there's more specifics about our engagement with the U.N. Security Council," she said.  (Yonhap)