The chief of an international group campaigning for an end to all nuclear testing has called on North Korea to reinstate its related moratorium, as speculation is rampant that the secretive regime may soon carry out an underground nuclear experiment.

"While I can assure you of the readiness of our verification regime to detect any nuclear test, I wish to take this opportunity to call on the Democratic People's Republic of Korea to renew the commitment it made in 2018 to suspend nuclear testing," Robert Floyd, executive secretary of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), said in a statement during a meeting of its governing body in Vienna on Monday (local time).

He also urged Pyongyang to sign and ratify the Comprehensive Nuclear-Test-Ban Treaty (CTBT).

The North announced a self-imposed moratorium on nuclear and intercontinental ballistic missile tests in April 2018, two months before historic summit talks with the United States in Singapore. In late 2019, however, the North's leader Kim Jong-un stated that Pyongyang no longer felt bound by the moratorium amid a stalemate in the denuclearization talks.

North Korea conducted its sixth and last nuclear test in September 2017 at the Punggye-ri site. South Korean and US intelligence communities say preparations for another test already have been completed. (Yonhap)