North Korea fired multiple short-range ballistic missiles towards the sea off its east coast on Friday, South Korea's military said, the latest in series of weapon tests carried out by Pyongyang in recent months.

South Korea's Joint Chiefs of Staff said the projectiles were fired from the east coast town of Wonsan, while Japan's public broadcaster NHK reported a short-range missile appeared to have been launched and had already fallen, citing a government official.

North Korea has launched ballistic and cruise missiles as well as tactical rockets in recent months, describing them as part of a program to upgrade its defensive capabilities.

Earlier on Friday, the powerful sister of North Korean leader Kim Jong Un said its tactical weapons were intended solely as a deterrent against South Korean military aggression, while again denying that Pyongyang was exporting the weapons.

US and South Korean officials have accused the North of shipping weapons to Russia to help Moscow replenish stocks for use in its war against Ukraine. Moscow and Pyongyang have denied the accusation.

Friday's missile launches come at the same time as a visit by Russian President Vladimir Putin to the Chinese northeastern city of Harbin.

Putin and Chinese President Xi Jinping criticized Washington and its allies for what the leaders called "intimidation in the military sphere" against North Korea at a meeting in Beijing on Thursday.

South Korea's air force has said US and South Korean stealth fighters conducted "intense" joint exercises on Thursday in the central region to test and enhance offensive and defensive maneuverability.