North Korea said today it had performed its first-ever nuclear weapons test, a move that prompted swift international condemnation, with the prime minister, Tony Blair, describing it as a “completely irresponsible act”. The underground explosion at 2.36am BST, which followed a warning by Pyongyang last week that it was planning such as test, was a complete success and a “great leap forward” for the reclusive communist state, its official KCNA news agency said. “It marks a historic event as it greatly encouraged and pleased the (North Korean army) and people that have wished to have powerful self-reliant defence capability,” KCNA said. The test was performed “with indigenous wisdom and technology 100%”, the agency said, adding that no radiation leaked from the site. There was no independent verification of the test, but South Korea’s seismic monitoring centre recorded a tremor registering 3.6 on the Richter scale at the time of the supposed blast, saying this was not a natural occurrence. Meanwhile, Russia’s ITAR-Tass news agency quoted a senior military official, Lieutenant General Vladimir Verkhovtsev, as saying it was “100% sure” that the country’s neighbour had carried out a nuclear test. This would make North Korea the ninth country known to have…