North Korea fired several cruise missiles toward the Yellow Sea on Saturday, Seoul's military said, days after South Korea and the US wrapped up their major joint military drills.

The Joint Chiefs of Staff announced the North's launch took place at around 4 a.m. but did not elaborate further, pending an analysis.

"While strengthening our monitoring and vigilance, our military is maintaining a full readiness posture in close cooperation with the US," the JCS said in a text message sent to reporters.

South Korea and the US wrapped up the 11-day Ulchi Freedom Shield exercise on Thursday. The North has denounced the drills as a rehearsal for invasion.

As part of the UFS, South Korea and the US have staged combined air drills, involving at least one US B-1B strategic bomber, above the Korean Peninsula.

In response, North Korea launched a military command post drill involving the scenario of occupying South Korean territory and fired two short-range ballistic missiles toward waters off its east coast earlier this week.

The North claimed the missile launch on Wednesday night was a tactical nuclear strike drill simulating "scorched-earth" strikes against major command centers and airfields in South Korea.

In March, North Korea said it launched strategic cruise missiles "tipped with a test warhead simulating a nuclear warhead."

At that time, the North's state media said two "Hwasal-1"-type strategic cruise missiles and two "Hwasal-2"-type strategic cruise missiles, launched in South Hamgyong Province, accurately hitting targets set in the East Sea. (Yonhap)