VIENNA: The group working for a ban on nuclear tests said on Monday it had detected an "event" registering 4.0 on the Richter Scale in North Korea, which announced earlier it had carried out an atomic test.
"We have shared with our state signatories information about a 4.0 magnitude event at 0135 GMT," Tibor Toth, the executive secretary of the Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO), said from New York.
The CTBTO is not qualified to make public statements on the nature of the incidents registered by its monitoring systems, and therefore did not confirm whether or not an explosion had taken place.
However, Toth said he had transferred data on the event to the organisation's 176 member states.
Pyongyang said Monday it had carried out its first test of an atomic bomb in what the official Korean Central News Agency described as a "historic event" aimed at bettering peace and security.
The underground blast, which was criticised around the world , defied international pressure to keep the secretive regime from becoming one of the world's nuclear powers.
It came just three days after a unanimous call from the UN Security Council, including China, for North Korea to abandon plans for testing a nuclear weapon.