TV images of North Korean short-range rocket launched 23 March. The North has launched dozens of short-range rockets in recent weeks.
North Korea launched two projectiles presumed to be ballistic missiles into the sea on Sunday, South Korea said.
The latest in a series of test-firings is seen as expressions of anger over its failure to win talks on receiving outside aid, and over ongoing US-South Korean military drills.
The projectiles were fired from the North Korean city of Kaesong near the border with the South and had a range of about 500 kilometers (311 miles), said a South Korean Joint Chiefs of Staff official who spoke on condition of anonymity because of department rules.
North Korea regularly conducts test-firings, but this year has seen an unusually large number of launches. South Korean officials have confirmed about 90 test-firings of missiles, artillery and rockets by North Korea since February 21. More than 10 of them have been ballistic launches.
North Korea also has recently pushed South Korea to accept a set of proposals that it said would reduce bilateral tensions, including the cancellation of regular military drills between Seoul and Washington that Pyongyang insists are preparation for a northward invasion.
Many in South Korea have doubts over how sincere the North is about its push to reduce tensions, and analysts see the pressure for better ties as meant in part to eventually win outside aid and investment.
South Korea has rejected the North's proposals, saying it must first demonstrate that it is serious about nuclear disarmament if it truly wants peace.
North Korea likely possesses a small arsenal of crude nuclear bombs and is working to build an arsenal of nuclear-tipped missiles that could reach the US mainland.
The two Koreas are divided along the world's most heavily fortified border. The Korean Peninsula officially remains in a state of war because the 1950-53 Korean War ended with an armistice, not a peace treaty.