North Korea test-fired two ballistic missiles on Monday, with one possibly experiencing an abnormal flight, according to South Korea’s military.

This occurred a day after North Korea vowed “offensive and overwhelming” responses to a new U.S. military drill with South Korea and Japan.

The missiles were launched 10 minutes apart from Jangyon in southeastern North Korea.

The first missile flew 370 miles, while the second flew only 75 miles, suggesting it might have crashed inland, CBS News has reported.

South Korean media reported that the first missile landed off the eastern city of Chongjin, while the second’s debris likely scattered on the ground. An analysis of the second missile’s launch is ongoing.

Written by B.C. Begley