North Korea fired artillery shots into the sea near a disputed maritime border with South Korea early Saturday, Seoul’s military reportedly said. Pyongyang’s artillery drill prompted alarm among South Korean residents living close to the border, but the shells did not fly across the border, according to reports.

The artillery shots, which were heard from the island of Baengnyeong, were probably aimed in a northwestern direction from the North's shore as part of a drill, a South Korean defense ministry official, who did not want to be named, told Reuters.

Tensions between the two Koreas have escalated since North Korea’s nuclear test in January and its long-range rocket launch earlier this month. Pyongyang’s recent activities have been slammed by South Korea and the United States, who have called them grave violations of U.N. Security Council resolutions. South Korea also suspended operations at the jointly run Kaesong industrial park in the North, following the latter’s provocative actions.

The South's office of the Joint Chiefs of Staff reportedly said that several rounds of shots were fired, revising the previous comments of the ministry official who said that only a single shot had been fired.

Meanwhile, Seoul's Defense Ministry said Saturday that the military completed its search operations for debris from the three-stage rocket North Korea launched on Feb. 7, South Korea's Yonhap News Agency reported. The ministry said that the navy recovered two pieces of debris presumed to be from the launch.

"It is difficult to collect other debris as they are dispersed in small pieces throughout the water. We believe there are no more significant debris left," a South Korean military official said, according to Yonhap.

North Korea's recent rocket launch, which put a satellite in orbit, has been seen by world powers as a disguise for developing an intercontinental ballistic missile that can deliver a nuclear bomb.