A rare quake of magnitude 5.9 struck North Korea off its east coast and a nuclear detonation has been ruled out as the cause.
The authorities said that the quake hit early in the morning at a depth of 538 km below the seabed. South Korea's Defence Ministry said there was no indication that North Korea had carried out a nuclear test.
The tremor occurred 176 kilometers east-southeast of Hoemul-li, North Korea, at a depth of 537.6 km below the East Sea, it said on its website. "It's a natural quake", John Bellini, a geophysicist at the USGS National quake Information Center, told Yonhap by phone.
North Korea has staged five nuclear tests - including two past year - and has made a significant progress in its missile capability under leader Kim Jong Un, who took power in 2011.
According to Reuters, shortly after the situation stabilized, the experts took into consideration the possibility the natural phenomenon could've been triggered by a new nuclear test.
It was initially reported as a magnitude 6.0 but was later revised to 5.8.
Ultimately, the communist nation aims to build an ICBM capable of hitting the continental U.S. with a nuclear warhead fitted on top.
The Hawaii-based Pacific Tsunami Warning Center issued no alerts as a result of the quake.