A 2.5 magnitude natural earthquake has struck North Korea's northeastern region, South Korea's state weather agency said Monday.

The quake occurred about 40 kilometers northwest of Kilju, North Hamkyong Province, at 11:57 p.m. Sunday, according to the Korea Meteorological Administration (KMA). Kilju is where North Korea's nuclear testing site is located.

The epicenter was at a latitude of 41.29 degrees north and a longitude of 129.13 degrees east at a depth of 15 km. The KMA said the quake occurred naturally.

The last quake in Kilju, which was also natural, was reported on April 19 at a magnitude of 2.7, according to the KMA.

Experts say the effect of past nuclear tests may be attributable to frequent natural quakes there in recent years.

Six nuclear tests were conducted in the Punggye-ri testing site in Kilju between 2006 and 2017. North Korea closed down the site in May 2018, ahead of the Washington-Pyongyang summit held on June 12, 2018. (Yonhap)