School students evacuate their dormitory building after an earthquake in Busan, South Korea, Sept. 12, 2016. (Xinhua/Newsis)

SEOUL, Sept. 12 (Xinhua) -- A 5.8-magnitude earthquake jolted southeastern South Korea on Monday, the biggest-ever quake striking the country, injuring at least two people and making people feel the tremor nationwide, the weather agency said.

The tremor came less than an hour after a 5.1-magnitude earthquake struck on the outskirts of Gyeongju city in North Gyeongsang province at about 7:44 p.m. local time (1044 GMT).

The epicenter of the first quake, which posted the country's fifth-biggest magnitude, was some 9 km southwest of the city, Yoo Yong-kyu, head of the Korea Meteorological Administration (KMA)'s quake and volcano section, said in a televised press briefing.

The second tremor with the highest-ever magnitude occurred at 8:32 p.m. at a nearby location, just 1.4 km away from the first epicenter.

South Korean high school students leave their school after an earthquake in Ulsan, South Korea, Sept. 12, 2016. (Xinhua/AFP PHOTO)

It was the biggest-ever quake that happened on the Korean Peninsula. The previously strongest tremor happened at a northwestern region in the Democratic People's Republic of Korea (DPRK) in January 1980.

Two people were injured in Gyeongju city, and no more injuries have been reported yet.

At least 22 aftershocks with two to four magnitudes followed the big quakes. The weather agency sees no possibility for tsunami.

The tremor was felt nationwide from adjacent cities of Ulsan and Busan to as far north as capital Seoul and far south as the southern resort island of Jeju.