South Korea's military says North Korea fired three short-range ballistic missiles from the country's east coast on Wednesday morning.

It says that one of the three missiles crossed the de facto maritime border set up by the United Nations and fell near South Korea's territorial waters for the first time.

South Korea's Joint Chiefs of Staff said the missiles were fired from near Wonsan in North Korea's eastern region at about 8:51 a.m.

It said one of the missiles crossed the Northern Limit Line and landed in international waters 167 kilometers northwest of Ulleungdo Island, off the coast of North Gyeongsang Province in eastern South Korea.

The military issued an air-raid warning for areas centered around Ulleungdo Island at about 8:55 a.m. Local residents were ordered through TV broadcasts and other means to evacuate underground or elsewhere.

President Yoon Suk-yeol called an emergency meeting of the National Security Council.

Since the start of this year, North Korea has been launching missiles with unprecedented frequency. It fired two short-range ballistic missiles toward the Sea of Japan on Friday.

The South Korean and US militaries are conducting a large-scale air drill that is scheduled to end on Friday. Pyongyang has repeatedly called for a halt to the exercise.

South Korea and the United States are on the alert for further provocations by North Korea.