North Korea fired off two short-range ballistic missiles into the sea from an inland site on Wednesday, the Joint Chiefs of Staff (JCS) in South Korea said Wednesday, the latest in a series of launches in recent months.

The launches come hours before U.S. Secretary of State John Kerry was to meet with his Chinese counterpart in annual high-level talks in Beijing to discuss a broad range of bilateral issues.

North Korea's missile and nuclear program could be also on the agenda.

The communist North fired two short-range missiles "presumed to be Scud-type ones into the East Sea from an air base in the North's western province of Hwanghae at 4 a.m. and 4:20 a.m.," JCS spokesman Um Hyo-sik said.

They flew some 500 kilometers and landed in international waters, he said, adding the North did not impose a no-fly, no-sail zone ahead of its missile launches.

"The North appears to be issuing a threat that it can fire missiles anywhere and at any time," another JCS officer said.

South Korea's military has stepped up vigilance against additional launches and is in a state of full readiness, according to the JCS.

It marks the first time in nearly two decades that the North fired off the missiles from an inland area, not a coastal one.

Wednesday's firing is the 13th time the North has launched rockets in 2014 and the fifth ballistic missile launch this year.

It also came a week after the communist country fired two short-range projectiles into the East Sea. (Yonhap)