Japan's government also reported the launch on Monday, with chief cabinet secretary Hirokazu Matsuno condemning the launches as a threat to the region's peace and security.
In less than two weeks, nuclear-armed North Korea has conducted three other missile tests, an unusual frequency of launches.
Two of those involved single "hypersonic missiles" capable of high speeds and manoeuvring after launch, while the last, on Friday, involved a pair of short-range ballistic missiles fired from train cars.
Monday's launch appeared to involved two SRBMs fired east from Sunan Airfield in Pyongyang, South Korea's Joint Chiefs of Staff said in a statement.
North Korea had used the airport to test fire the Hwasong-12 intermediate-range ballistic missile in 2017.
The latest launches have drawn both condemnation and an appeal for dialogue from a US administration that has imposed new sanctions over North Korean missile launches and is pushing for more.
US President Joe Biden's administration imposed its first new sanctions on Pyongyang on Wednesday, and called on the UN Security Council to blacklist several North Korean individuals and entities.
It also repeated calls for Pyongyang to return to talks aimed at reducing tensions and persuading it to surrender its arsenal of nuclear weapons and ballistic missiles.
North Korea has defended the missile tests as its sovereign right to self-defence and accused the United States of intentionally escalating the situation with new sanctions.
In a statement before Friday's missile tests, the North Korean foreign ministry said that although Washington might talk of diplomacy and dialogue, its actions showed it was still engrossed in its policy of "isolating and stifling" North Korea.
The launches came as North Korea, more isolated than ever under self-imposed border closings aimed at preventing a COVID-19 pandemic, appeared to be preparing to open at least some trade across its land border with China.
Chinese brokers said they expect the resumption of regular trade with North Korea as soon as Monday after a North Korean train pulled into a Chinese border town on Sunday in the first such crossing since anti-coronavirus border lockdowns began in 2020.
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