The Joint Chiefs of Staff (JCS) said it detected what are presumed to be short-range missiles fired off the eastern coastal city of Wonsan at 3:10 p.m. toward the East Sea, Yonhap news agency reported.

"The North Korean missiles flew about 300 kilometres and landed in the East Sea," the JCS said.

The South Korean military denounced the latest missile launch as "a provocative act" that threatens security and stability on the Korean Peninsula and vowed a stern response to the North's provocations.

"Our military has ramped up monitoring and vigilance against additional launches while closely sharing information related to North Korean ballistic missiles with the US and Japanese authorities," the JCS said in a text message to reporters.

The launch comes after the North fired 600-mm super-large shells, considered to be short-range ballistic missiles, toward the East Sea on April 22.

North Korean state media said leader Kim Jong-un guided tactical drills simulating a nuclear counterattack involving "super-large" multiple rocket launchers for the first time.

Pyongyang's latest missile launch comes a day after two South Korean F-35As and two US F-22 Raptors carried out joint combat drills over the central region of South Korea in an apparent show of air power against evolving North Korean military threats.

On the same day, Russian President Vladimir Putin and Chinese President Xi Jinping issued a joint statement opposing "acts of military intimidation" against North Korea by the US and its allies during their summit in Beijing.

Earlier in the day, Kim Yo-jong, the sister of North Korean leader Kim Jong-un, dismissed allegations of military cooperation between Pyongyang and Moscow, emphasising the country's weapons are solely intended to target South Korea.