URGENT ¥¥¥ N. Korea nuclear test 'grave threat to Japan': PM

North Korea's nuclear test is a 'grave threat' to Japan, Prime Minister Shinzo Abe said Tuesday, hours after Pyongyang confirmed it had successfully detonated an atomic device.

"(The test) is a grave threat to the safety of our country and a serious challenge against the global framework of nuclear disarmament and non-proliferation," Abe said in a statement, adding it "cannot be tolerated".