The U.S. Department of Defense urged North Korea on Thursday to refrain from provocative actions as it confirmed that the communist nation fired a series of short-range rockets off its east coast earlier in the day.

The launches of five rockets coincided with the arrival of Pope Francis in the first papal visit to South Korea in 25 years. Three of them were fired about half an hour before the pope's arrival and the two others a couple of hours later.

The firings came days before South Korea and the United States were set to kick off annual joint military exercises Monday. Pyongyang condemns such maneuvers as a rehearsal for invasion of the country and the rocket launches were seen as an expression of anger by the North at the upcoming drills.

The Pentagon confirmed the launches, saying all of the rockets fell into the East Sea.

"We urge North Korea to refrain from provocative actions that aggravate tensions and instead focus on fulfilling its international obligations and commitments. We are closely monitoring the situation on the Korean Peninsula," said Lt. Col. Jeff Pool in response to Yonhap News Agency's request for comment.

"We continue to urge North Korea to exercise restraint and take steps to improve its relations with its neighbors. The onus is on North Korea to refrain from provocations," he said.

Thursday's firings marked the 17th time the North has fired rockets or missiles this year. Since February, the North has fired a total of 107 rockets and short- or medium-range missiles.

Some of them were ballistic missiles that Pyongyang is banned from launching under U.N. resolutions. (Yonhap)