(ATTN: UPDATES headline, lead, throughout with details)
SEOUL, Sept. 12 (Yonhap) -- A record magnitude-5.8 earthquake jolted South Korea's southwestern region, the country's meteorological agency said Monday.
The quake detected at 8:35 p.m. was the strongest tremor reported on land in the country with the Korea Meteorological Administration (KMA) saying the epicenter was near Naenam-myeon region in Gyeongju, some 371 kilometers southeast of Seoul.
The quake was preceded by a 5.1-magnitude tremor detected at 7:44 p.m. in the same area located some 9 kilometers south of Gyeongju. The second quake was felt in most parts of the country.
No serious damage was immediately reported, including at the Wolsong, Hanul and Gori nuclear power plants located in the Gyeongsang region.
Korea Hydro & Nuclear Power Co., which operates the country's nuclear plants said none of its reactors were affected and producing electricity.
Most people in the region near the quakes center felt homes and buildings shake violently, with residents living in an 80-story highrise in South korea's largest port city of Busan saying they felt the building shudder.
The Ministry of Public Safety and Security said it did not receive reports of major damage or serious injuries, although there was a spike in people calling authorities to find out about the quake.
It said there were reports of people scared by the tremor evacuating buildings, with some refraining from using elevators.
Authorities also said a few KTX bullet trains halted operations, while South Korea's most-used mobile messenger KakaoTalk went offline shortly after the quake in Gyeongju.
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