SEOUL » North Korea on Monday fired four short-range projectiles into the sea, Seoul officials said, in a continuation of weapon launches the country has carried out in an apparent response to ongoing South Korea-U.S. military drills it sees as a provocation.

The projectiles launched from the northeastern city of Hamhung flew about 125 miles before landing in waters off North Korea’s east coast, South Korean defense officials said on condition of anonymity, citing department rules.

Monday’s launches came three days after Seoul said North Korea launched its first medium-range missile into the sea since early 2014.

South Korea’s Yonhap news agency earlier reported that a missile had been fired, but later changed that to say that projectiles had been fired.

The firings appear to be North Korea’s response to the annual springtime military exercises that it says are an invasion rehearsal. Earlier this month, North Korea fired several short-range missiles and artillery shells into the sea and threatened pre-emptive nuclear strikes against Washington and Seoul.

The drills are the largest ever, and come after the North’s nuclear test and long-range rocket launch earlier this year.

North Korean leader Kim Jong Un recently ordered tests of a nuclear warhead explosion and ballistic missiles capable of carrying nuclear warheads.