SEOUL - A nuclear reactor at South Korea's Younggwang Nuclear Power Plant automatically shut down on Monday after reactor protection signals had been detected, local media reported.

The state-run Korea Hydro & Nuclear Power Co (KHNP) said the Unit 3 reactor at the Younggwang plant, located some 330 kilometers southwest of Seoul, went off-line at 2:57 pm (local time).

"An investigation is currently under way to confirm what has exactly caused the automatic shutdown of the reactor," an official from the KHNP was quoted by Yonhap news agency as saying.

There was no release of radioactivity and the safety of the nuclear power plant showed no major problems.