All three flew at an altitude of around 100 km (62 miles) and covered a range of around 350 km (217 miles), Japan's defence ministry said. South Korean military also said the missiles flew about 350 km.
"North Korea's ballistic missile(s) launch is a grave provocation that undermines peace and stability on the Korean Peninsula as well as the international community," South Korea's Joint Chiefs of Staff said, condemning it as a clear violation of the U.N. Security Council resolution and urging it to stop immediately.
US Indo-Pacific Command said the latest launches did not pose an immediate threat to US personnel or territory, or to Washington's allies, but they highlighted the destabilising impact of North Korea's weapons programme.
The launches came a day after South Korea's defence ministry announced it had successfully conducted a test flight of a solid-propellant space launch vehicle.
On Monday, five North Korean drones crossed into South Korea, prompting the South's military to scramble fighter jets and attack helicopters to try to shoot them down, in the first such intrusion since 2017.
Relations between North Korea and US-ally South Korea have grown more tense since South Korean President Yoon Suk-yeol's conservative government took over in May, promising a tougher stance toward the North.
Not counting Saturday's launches, North Korea has fired around 70 ballistic missiles this year, Yonhap news agency said, including about eight intercontinental ballistic missiles (ICBM).
North Korean state media KCNA had yet to mention the launches, but said on Saturday that leader Kim Jong Un had presided over a party meeting on Friday to decide policy and strategy for 2023.