The United States is aware of reports that North Korea has launched a short-range projectile, a senior US government official said Wednesday, declining to comment further.

Earlier, South Korea's Joint Chiefs of Staff said the North had fired two projectiles from near its east coast city of Wonsan on Thursday (Seoul time). The projectiles flew about 430 kilometers and landed in the East Sea, it said.

"We are aware of reports of a short-range projectile launched from North Korea," the official told Yonhap News Agency, referring to one, not two, projectiles. "We have no further comment."

The South's JCS said the allies are in the process of determining the exact nature of the projectiles.

The launch comes as Washington has sought to restart working-level negotiations on dismantling the North's nuclear weapons program in line with an agreement reached between US President Donald Trump and North Korean leader Kim Jong-un at their impromptu meeting at the inter-Korean border on June 30.

The last time North Korea fired projectiles was on May 9 when it launched two short-range missiles into the East Sea in an apparent show of frustration over stalled talks with the US.

Last week, the North warned that the resumption of working-level talks would be affected by whether Seoul and Washington go ahead with joint military exercises planned for next month.

North Korea denounces the drills as a rehearsal for invasion. (Yonhap)