It is the second launch carried out by the North Korean regime since Saturday and according to Pyongyang, it is in retaliation to the joint military operations being carried out by South Korea and the United States.
North Korea fired two short-range ballistic missiles on Monday, Pyongyang's second launch in 48 hours as Kim Jong Un's powerful sister warned of turning the Pacific into a "firing range", Seoul says.
South Korea's military said they had detected the launch of "two short-range ballistic missiles fired from Sukchon areas in South Pyongan province between 07:00-07:11 local time."
Tokyo also confirmed the launch, with the Prime Minister's Office warning that Pyongyang had launched "a suspected ballistic missile" and the coastguard issued alerts over multiple projectiles.
North Korea issued a statement saying it had "fired two shots using 600mm multiple rocket launchers", into the East Sea, also known as the Sea of Japan.
The launch comes less than 48 hours after Pyongyang conducted what it called a "surprise" drill to fire an Intercontinental Ballistic Missile (ICBM) Saturday, which it said demonstrated North Korea's capacity to carry out a "fatal nuclear counterattack".
Japan said Saturday's ICBM had flown for 66 minutes and landed in its exclusive economic zone (EEZ). In response, Seoul and Washington staged joint air drills on Sunday, featuring a strategic bomber and stealth fighter jets.
In a statement issued early Monday, North Korean leader Kim's sister Kim Yo Jong warned that Pyongyang would continue to take "corresponding counteraction" to any perceived threats.
"The frequency of using the Pacific as our firing range depends upon the US forces' action character," she said in a statement carried by the official KCNA, which also strongly criticised outside assessments of Saturday's ICBM launch.
Relations between the two Koreas are at one of their lowest points in years, after North Korea declared itself an "irreversible" nuclear state and leader Kim called for an "exponential" increase in weapons production, including tactical nuclear weapons.