North Korea's state media KCNA reported that the country tested a super-large multiple rocket launcher on Saturday.
Norther Korea fired one short-range ballistic missile into the sea, the South Korean military reported, according to the Yonhap news agency.
The New Year's Day firing was the second in as many days and continued a record-breaking blitz of launches in 2022.
North Korea's series of missile tests are grave provocations that hurt peace and stability of the Korean peninsula and beyond, South Korea's military said, urging Pyongyang to stop them.
The projectile came from the Yongseong area of the capital Pyongyang and landed in the East Sea, also known as the Sea of Japan, Yonhap said, quoting the Joint Chiefs of Staff.
Military tensions on the Korean peninsula rose sharply in 2022 as the North conducted sanctions-busting weapons tests nearly every month, including firing its most advanced intercontinental ballistic missile ever.
Today, the North fired three short-range ballistic missiles, Seoul's military said, a day after South Korea successfully tested a solid-fuel space launch vehicle.
Japan's coast guard said the missile reached an altitude of around 100km and flew around 350km before landing outside of Japan's exclusive economic zone.
Japanese Defence Minister Yasukazu Hamada told reporters that Tokyo had protested to North Korea over the launch via diplomatic channels in Beijing.
That North Korean launch also followed the incursion of five North Korean drones into the South's airspace earlier in the week.
Monday's North Korean drone incursion was the first such incident in five years and prompted an apology from Seoul's defence minister after the military failed to shoot down a single drone despite scrambling jets for a five-hour operation.
Party meeting
North Korea is currently holding a major party meeting in Pyongyang at which North Korean leader Kim Jong Un and other senior party officials are outlining their policy goals for 2023 in key areas including diplomacy, security and the economy.
Earlier this year, Mr Kim said he wanted his country to have the world's most powerful nuclear force and declared the North an "irreversible" nuclear state.
On Wednesday, Mr Kim set out "new key goals" for the country's military, state media reported, without giving any specifics.
North Korea's end-of-year plenary meetings are typically used by the regime to unveil the country's domestic and foreign policy priorities for the year ahead.
Full details of the current session are expected to be announced after it concludes.
