North Korea fired four short-range ballistic missiles into the western sea on Saturday morning, the South Korean military said, adding the missiles flew about 130 km (80 miles) at an altitude of about 20 km (12 miles).
North Korea has launched a series of missiles this week, including a possible failed intercontinental ballistic missile (ICBM), drawing condemnation from Washington, Seoul and Tokyo and raising speculation it could be readying for the resumption of nuclear testing for the first time since 2017.
Saturday's launch, fired between 11:31 a.m. and 11:59 a.m. local time, comes as the United States and South Korea wrapped up a six-day Vigilant Storm exercise that began on October 31.
The joint military exercise involved some 240 military aircraft and two US strategic bombers B-1B, according to South Korea's Joint Chiefs of Staff.
This is the first time the B-1B has been deployed in US-South Korean drills since 2017, which shows "the combined defense capabilities and determination of the Republic of Korea and the US to resolutely respond to any provocations from North Korea, and the will of the US to implement a strong commitment to extended deterrence," JCS said in a statement.
Pyongyang on Friday demanded that the United States and South Korea halt "provocative" air exercises. South Korea said it scrambled warplanes in response to 180 North Korean military flights near the countries' shared border on Friday.
The recent North Korean missile tests
On Wednesday, North Korea fired a daily record 23 missiles, with one landing off the coast of South Korea for the first time.
In recent years the UN Security Council has been split on how to deal with North Korea and in May, China and Russia vetoed a US-led push to impose more UN sanctions in response to North Korean missile launches.