Two seismic events recorded in North Korea were probably aftershocks from the state's missile test on 3 September, experts say.

When the tremors were first reported earlier, China said it believed they may have been caused by an explosion.

But the country's earthquake monitoring centre later went on the say a magnitude 3.4 earthquake was not the result of a fresh missile test.

Lassino Zerbo, of nuclear watchdog the Comprehensive Test Ban Treaty Organisation (CTBTO), tweeted that the quake was not man-made but similar to a "collapse" event, or tremor, that followed almost immediately after the 3 September test.

"The most probable hypothesis at present is that this is a consequence of the previous event, which was of a significant magnitude and may still have repercussions in a fracture zone," Mr Zerbo told the AFP news agency.


Image: The tremor was detected near where North Korea recently conducted a nuclear test

The latest alert comes amid heightened tensions in the Korean peninsula.

On Friday, Donald Trump publicly branded the North Korean leader Kim Jong Un a "rocket man" and said American "really had no choice" but to confront the authoritarian regime.

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Previous earthquakes in North Korea have indicated nuclear tests by the nation, which is at loggerheads with the US and the rest of the international community over its weapon development.

The site of the 3.4 tremor is close to where the regime claimed to have detonated a thermonuclear weapon on 3 September, in its sixth and most powerful nuclear test to date.

Mr Trump later used his speech to the UN General Assembly to tell the world he would "totally destroy" North Korea if the USA was threatened by its regime.

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Mr Kim branded the speech the "most ferocious declaration of war in history" and said he would consider the "highest level of hardline countermeasure" in response.

Tens of thousands of people reportedly took part in an anti-America march in Pyongyang on Friday.

And US bombers and fighter jets have flown along the coast of North Korea in a show of force.