The National Security Office(NSO) of the presidential office held a security meeting right after North Korea fired two short-range ballistic missiles late Monday.

The meeting, chaired by second deputy national security adviser Lim Jong-deuk, included a briefing from the Joint Chiefs of Staff(JCS) on the missile launches and North Korean military movements and a check on the readiness posture of the South Korea-U.S. alliance.

The pair of missiles, detected by the JCS from areas near Pyongyang between 11:55 p.m. and 12 a.m. Tuesday, flew about 400 kilometers to eastern waters.

The NSO reportedly assessed that the North made the latest provocation to protest a port call by a nuclear-powered U.S. submarine, the USS Annapolis, to Jeju Island on Monday.

The visit comes about a week after another nuclear-powered submarine, the USS Kentucky, docked at a port in Busan, prompting the North to fire several cruise missiles on Saturday.