SEOUL, South Korea (CNN) — North Korea test-fired a fourth short-range missile off its east coast Thursday, South Korea’s Yonhap News Agency reported. South Korea’s Defense Ministry had earlier confirmed three launches, but could not immediately be reached about the fourth reported missile. The first three missiles were fired at 5:20 p.m., 6 p.m., and 7:50 p.m. local time from Sinsang-ni near the eastern coastal city of Wonsan, a ministry spokesman said. A U.S. official told CNN “the missile firings come as no surprise.” “The North has been carrying out provocative acts for some time,” said the official, who did not want to be named for security reasons. “North Korea needs to stop this type of activity and return to the process of bringing about a denuclearization of the Korean peninsula.”