VIENNA - An international nuclear test monitoring agency said on Tuesday an unusual seismic event detected in North Korea showed "clear explosion-like characteristics."

Tibor Toth, executive secretary of the Comprehensive Nuclear Test Ban Treaty Organisation (CTBTO), also said the event's location was "roughly congruent with" nuclear tests carried out by North Korea in 2006 and 2009.

"For now, further data and analysis are necessary to establish what kind of event this is. If confirmed as a nuclear test, this act would constitute a clear threat to international peace and security, and challenges efforts made to strengthen global nuclear disarmament and non-proliferation, in particular by ending nuclear testing," he said in a statement.

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