SEOUL, Sept. 29 (Yonhap) -- North Korea fired an unspecified ballistic missile into the East Sea on Thursday, South Korea's military said, in the third provocation this week by the recalcitrant regime.

The Joint Chiefs of Staff (JCS) announced the launch, hours after U.S. Vice President Kamala Harris wrapped up a daylong visit to South Korea, during which she met with President Yoon Suk-yeol and toured the Demilitarized Zone (DMZ) bisecting the two Koreas. She reaffirmed America's security commitment to the East Asian ally.

The North fired a short-range ballistic missile (SRBM) on Sunday and two SRBMs on Wednesday.

The latest launch came as South Korea and the United States concluded a high-profile naval exercise, involving the USS Ronald Reagan aircraft carrier in the East Sea, on Thursday and are set to hold an anti-submarine training with Japan the following day.

Seoul and Washington have been cranking up security coordination amid concerns that Pyongyang could engage in provocative acts, such as a nuclear experiment and a submarine-launched ballistic missile test.