North Korea has fired two unidentified ballistic missiles, the South Korean military said on Monday.
North Korea launched the missiles from Jangyon, South Hwanghae Province, South Korean news agency Yonhap cited the general staff in Seoul (JCS) as saying.
One missile flew about 600 kilometres, while the second flew about 120 kilometres, Yonhap reported.
The launch came as North Korea warned of countermeasures against a joint military exercise held by South Korea, the United States and Japan.
North Korea would "firmly defend the sovereignty, security and interests of the state and peace in the region through offensive and overwhelming countermeasures," a statement carried by Pyongyang's state-controlled KCNA news agency said.
Pyongyang regularly accuses Washington and Seoul of preparing for an attack with their military exercises, which both countries deny.
Tensions on the Korean Peninsula have again risen in recent months.
Widely isolated North Korea, under the rule of Kim Jong Un, is subject to international sanctions because of its nuclear weapons and missile programme.
Despite the sanctions, North Korea has for years been advancing the development of missiles, especially nuclear-capable missiles.
On Thursday, North Korea claimed to have successfully tested a missile capable of carrying multiple warheads, although these were dismissed by South Korea as deceptive and exaggerated.
KCNA news agency spoke of a successful test for a "new important technology." However a spokesman for the JCS told journalists in Seoul that the test missile, fired by North Korea the day before, had exploded in the early phase of the flight.