North Korea said its nuclear test Tuesday was only a "first" step and warned of stronger action if it was faced with tougher sanctions as a result."The latest nuclear test was only the first action, with which we exercised as much self-restraint as possible," the foreign ministry said in a statement carried by the country's official news agency.
"If the U.S. further complicates the situation with continued hostility, we will be left with no choice but to take even stronger second or third rounds of action," it said without elaborating.
The statement came just hours after South Korea's spy agency chief warned Pyongyang might carry out another nuclear test or ballistic missile launch in the coming days or weeks.
North Korea said Tuesday's test was directly targeted at the United States. It accuses Washington of inciting global condemnation of its nuclear program and of leading the sanctions charge in the U.N. Security Council.
Its claim of miniaturization suggests that it is a step closer to fitting a nuclear warhead onto a ballistic missile.