"The United States is deeply troubled that North Korea has decided to launch these missiles during a delicate time in the six- party talks," National Security Council spokesman Gordon Johndroe said in a statement.

The launches were "a violation of UN Security Council Resolution 1718, which prohibits North Korea from engaging in all ballistic missile activities," Johndroe said.

The spokesman urged Pyongyang to "refrain from conducting further provocative ballistic missile launches," which, he said, destabilize the security of northeast Asia.

But he did not reveal how many missiles the DPRK launched.

Prior to the statement by Johndroe, Yonhap news agency said the DPRK appeared to have test-fired a short-range missile into the Sea of Japan on Wednesday as part of a routine military exercise.

The latest missile test by Pyongyang occurred when it announced on Monday that the frozen fund dispute with the United States has been resolved, vowing it will start implementing the disarmament deal struck in February.

The DPRK test-fired in July last year seven missiles, including the Taepodong-2, which could theoretically reach the U.S. west coast. Those launches brought UN condemnation and missile-related sanctions.