North Korea appears to have launched a ballistic missile from a submarine Saturday evening, South Korea’s joint chiefs of staff said.

The missile was fired from a submarine off North Korea’s east coast, in the Sea of Japan, about 6:30 p.m. local time, the joint chiefs said. The missile flew for only about 20 miles, well short of a submarine-launched ballistic missile’s minimum range of 200 miles, Yonhap News Agency reported.

North Korea said last May that it had successfully test-fired a submarine-launched ballistic missile from under the sea, with the state news agency reporting that leader Kim Jong Un had ordered the test of the “world-level strategic weapon” and was present when it “soared into the sky from underwater.”

North Korea also released photos of the event, including one that showed Kim on a boat holding binoculars as the rocket blasted out of the sea. But missile experts later said that the launch was faked and that the pictures had been doctored.

As Kim’s regime prepares for a much-hyped communist Workers’ Party congress early next month, analysts have been expecting Pyongyang to stage more provocations to give Kim more to crow about. A party congress has not been held since 1980, and Kim, 33, is expected to use the meeting to bolster his legitimacy as the third-generation leader of North Korea.

Tensions with the country have run high since Kim ordered a nuclear test in January, swiftly followed by a long-range rocket launch that scientists say appeared to be part of an intercontinental ballistic missile program.

South Korean military officials warned earlier Saturday that North Korea could be preparing to carry out a fifth nuclear test. They had seen vehicles and people moving at the Punggye-ri nuclear test site in the northeast of the country.

Separately, North Korea’s foreign minister, Ri Su Yong, said that his country is prepared to stop its nuclear tests if the United States suspends its annual military exercises with South Korea.

“Stop the nuclear war exercises in the Korean Peninsula, then we should also cease our nuclear tests,” Ri told the Associated Press in an interview in New York, where he participated in signing the Paris agreement on climate change at the United Nations.

While defending North Korea’s right to maintain a nuclear deterrent and saying that the regime would not be bullied by international sanctions, Ri suggested that suspending the military exercises could open the door to reduced tensions, the AP reported.