PYONGYANG, North Korea - A magnitude 6.0 earthquake struck off the coast of North Korea on Thursday, sparking fears that Pyongyang had detonated another nuclear bomb.

The quake that struck very deep, 348.2 miles (560 km) below the seabed, had experts pointing out that it was unlikely to have caused any damage. 

The epicentre of the quake was 125 miles (201 km) south-east of the North Korean city of Chongjin and later in the day, experts pointed out that it was indeed a genuine quake, not a man-made one caused by a nuclear test, like in previous situations. 

North Korea's previous five nuclear tests caused signs of artificial quakes, including in January last year, when a man-made earthquake was detected near a known nuclear testing site in the country.

The quake came amid heightened tensions surrounding the country's weapons programme.

According to the United States Geological Service, it was a 5.1 magnitude quake that South Korea said was 49 kms (30 miles) from the Punggye-ri site where the North has conducted nuclear tests in the past.

Experts explained that natural earthquakes create different seismic patterns from ones caused by humans.

South Korea's Defense Ministry also said there was no indication that North Korea had carried out a nuclear test.

According to Ik-hyun, any earthquake deeper than 43 miles normally causes little damage on the surface.

He explained that even if a ship was sailing over the epicentre at the time of the quake, it wouldn't have noticed anything.

Experts further pointed out that unlike in neighbouring Japan, earthquakes are rare on the Korean Peninsula.

Last year, on September 12, two quakes measuring 5.1 and 5.8 jolted southeastern South Korea, causing no casualties.

Following Pyongyang's July 4 test launch of its first intercontinental ballistic missile, tensions between U.S. and North Korea have hit an all time high.

Earlier in the day, North Korea threatened to turn the U.S. into a 'pile of ash' if U.S. President Donald Trump tries to use force to stop Pyongyang's nuclear programme.

North Korea's state-run newspaper Minju Choson warned that military intervention will "inevitably lead the U.S. to self-destruction."

The threat came after U.S. successfully tested its THAAD missile defense system against an intermediate-range ballistic missile in the Pacific Ocean near Hawaii and Alaska - a region that will be vulnerable if North Korea indeed succeeds at launching a nuclear attack on the U.S., as it has threatened.