SEOUL, South Korea — North Korea fired several ballistic missiles into the sea on Monday, South Korea’s military said, hours after South Korean and U.S. troops kicked off their large annual combined drills, which the North views as an invasion rehearsal.

North Korea has fired several ballistic missiles as South Korea and the United States initiated military drills. South Korea’s Joint Chiefs of Staff said on Monday that North Korea’s fifth launch event this year fired several missiles off the west coast into the sea.