South Korea’s military said North Korea fired at least one ballistic missile toward the East Sea early Wednesday morning; an action that took place ahead of the annual joint exercise between South Korea and the United States and is assessed by Pyongyang as a protest against the exercise.

According to South Korea’s Joint Chiefs of Staff, the missile was launched from the Wonsan area on North Korea’s eastern coast, and Seoul has increased its readiness level and surveillance in the event of further launches. South Korea, the United States, and Japan also said they will continue exchanging information and security coordination.

South Korea’s presidential office called the action “provocative” and demanded the immediate halt of missile launches. At the same time, South Korea, the United States, and 37 other countries, in a joint statement, asked countries that have ballistic missiles and space launchers to announce, at least 24 hours before each launch, the necessary information about the time, location, type, and route of the missile. The request was raised after a submarine-launched ballistic missile launch by China last month, although the statement did not mention China by name.