North Korea's claim that it successfully carried out an underground nuclear test Monday makes it the first country to do so since India and Pakistan detonated nuclear devices in May of 1998.
The Non-Proliferation Treaty officially recognizes China, France, Russia, Britain and the United States as having nuclear weapons. However, nine nations, including North Korea, are known or generally thought to posses nuclear arms.
North Korea is believed to have enough fissile material for about six weapons. Estimates vary, however, and have not been confirmed.
The United States and Russia have about 5,000 strategic warheads each.
The U.S. arsenal includes at least 1,000 operational tactical weapons, which are meant for the battlefield and are less powerful than strategic arms -- warheads that can be delivered by intercontinental missiles.
Russia has some 3,500 operational tactical warheads and at least 11,000 strategic and tactical warheads in storage.
France has about 350 strategic warheads, while Britain has about 200 similar devices.
China says it has 250 strategic warheads and 150 tactical warheads.
India boasts between 45 and 95 nuclear warheads, and neighboring Pakistan has between 30 and 50.
Israel refuses to confirm whether it has nuclear weapons. However, it is generally assumed the country has at least 200 nuclear warheads.
Some information for this report provided by AP and AFP.