South Korea's military said on Wednesday that it had "detected two short-range ballistic missiles fired from the Sunan area in Pyongyang," towards its eastern waters.
"Our military has reinforced monitoring and surveillance and is maintaining utmost readiness in close coordination with the United States," Seoul's Joint Chiefs of Staff said in a statement.
Wednesday's missiles were launched 10 minutes apart between 18:10 local time (09:10 GMT) and 18:20 (09:20 GMT) according to the Joint Chiefs of Staff.
They flew about 360 km (225 miles) and reached an altitude of 30 km (19 miles), they said, giving a maximum velocity of Mach 6 (4,600 mph or 7,450 kmh).
Japan's coast guard also identified a possible missile launch, citing the Defense Ministry, and cautioned vessels in the area to be aware.
The Japanese minister of state for defense, Toshiro Ino, condemned the launches as "unacceptable."
"North Korea's series of actions, including repeated ballistic missile launches, poses a threat to the peace and security of Japan, the region and international society," he told reporters.
Launches come on the eve of Harris visit
The reported missile launches come just days after Pyongyang fired another missile into its eastern waters and also comes ahead of US Vice President Kamala Harris's trip to South Korea on Thursday.
Harris is set to hold talks with President Yoon Suk Yeol, along with other senior officials. She will also visit the heavily foritifed Demilitarized Zone (DMZ) dividing the two Koreas.
The US and South Korea are currently conducting military drills off the east coast in a show of force against the North.
Four days of joint exercises involving the nuclear powered aircraft carrier USS Ronald Reagan began on Monday.
