The Democratic People's Republic of Korea (DPRK) fired several cruise missiles off the country's east coast on Wednesday, marking the fifth launch since the beginning of the year, South Korea's military said in a statement.

"Our military detected several unknown cruise missiles over the waters northeast of Wonsan around 09:00 today (1200 GMT) and South Korea-US intelligence authorities are conducting a detailed analysis," the Joint Chiefs of Staff said in a statement. 

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"While strengthening surveillance and vigilance, our military is cooperating closely with the United States and closely monitoring additional signs and activities from North Korea," it added.

The DPRK's state-run news agency KCNA reported on Monday that a new guided shell and control system for a multiple rocket launcher has been developed by the North Korean Academy of Defense Science. The outlet added that the system was also tested, pointing out that this update will "qualitatively change" the structure of the country’s multiple-launch rocket systems.

Earlier this year, leader Kim Jong Un declared South Korea as the DPRK's "principle enemy," warning Seoul of war for "even 0.001 mm" of territory violation.

Meanwhile, South Korean President Yoon Suk-Yeol ordered his Marine Corps to "act first, report later" if provoked.

The United States, Seoul, and Japan have increased their military cooperation and exercises in the past two years, which included coordination on a nuclear level, leading to heightened tensions both with Pyongyang and China.

In response, the DPRK increased its weapon testing activities since the new year to include underwater nuclear weapon testing and a solid-fuel hypersonic ballistic missile.

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