The South Korean military reported that on Saturday, as Seoul and Washington concluded a public six-day military exercise, North Korea launched four short-range ballistic missiles into the western sea.

The United States, South Korea, and Japan have all condemned North Korea for its recent missile launches, which include what may have been a failed intercontinental ballistic missile. There is speculation that North Korea may be getting ready to resume nuclear weapons testing for the first time since 2017.

The launches on Saturday between 11:31 and 11:59 a.m. (0231 and 0259 GMT) coincide with the conclusion of the “Vigilant Storm” exercise that South Korea and the US started on Monday.

According to Seoul, the missiles traveled roughly 130 km (80 miles) and reached a height of 20 km (10 miles).

According to South Korea’s Joint Chiefs of Staff, the allied exercise included 240 military aircraft, two American B-1B strategic bombers, four F-16 fighters, and four F-35A fighters.

This is the first time the B-1B has been deployed in U.S.-South Korean drills since 2017, showing “the combined defence capabilities and determination of the Republic of Korea and the U.S. to resolutely respond to any provocations from North Korea, and the will of the U.S. to implement a strong commitment to extended deterrence,” the joint chiefs said in a statement.

Pyongyang on Friday demanded 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.

On Wednesday, North Korea fired a daily record 23 missiles, with one landing off the coast of South Korea for the first time, after Pyongyang threatened to take powerful measures unless Washington halts allied air exercises with South Korea.

In response to the ongoing “tit-for-that” exchange, Washington requested a public Security Council meeting on Friday and accused Russia and China of shielding North Korea from more Security Council action.

Late on Friday, a spokesman for the North Korean foreign ministry warned that “continued provocation is bound to be followed by continuous counteraction,” according to state-run media KCNA.

The Security Council has disagreed in recent years about how to handle North Korea. A U.S. attempt to impose additional U.N. sanctions in response to North Korean missile launches was blocked in May by China and Russia.