SEOUL, Sept. 13 (Xinhua) — South Korean President Park Geun-hye on Tuesday ordered government officials to comprehensively review the country's earthquake response system after the biggest-ever tremor shook its southeastern region on Monday night.

Park chaired a cabinet meeting in the presidential office, instructing officials to thoroughly brace for possible quakes of higher seismic intensity than Monday's tremors by fully reviewing measures to protect major facilities, including nuclear power plants and radioactive waste disposal facilities, from violent quakes.

The president said the series of earthquakes became a wake-up call to the perception that South Korea is relatively a safe zone from earthquakes.

A 5.8-magnitude earthquake, the largest ever hitting the country, struck on the outskirts of Gyeongju city in North Gyeongsang province at about 8:32 p.m. local time (1132 GMT) on Monday.

The main shock occurred less than an hour after a quake with a magnitude of 5.1 rattled the nearby region.

The epicenters of the two quakes are located just 1.4 km away from each other southwest of Gyeongju, near which multiple nuclear power plants and a radioactive waste disposal facility are sited. The majority of the country's nuclear power stations are located along the east coast.

Korea Hydro and Nuclear Power (KHNP), the country's nuclear power operator, said its atomic power plants suffered no damage, but it turned off four nuclear reactors at the Wolsong nuclear power plant at around midnight for a safety inspection.

In the adjacent coastal city of Ulsan, a thermal power plant halted operations following the series of quakes.