North Korea has demolished a 20m tall cooling tower at its main Yongbyon nuclear reactor, in a sign of its commitment to stop making plutonium for atomic bombs.

The demolition came a day after Pyongyang handed China a long-delayed account of its nuclear programme and was seen as symbolic, as the reactor has already been disabled.

The Yongbyon complex, built around a Soviet-era nuclear reactor, is the North's only known source of plutonium, the New York Times reports. North Korea had started disabling the reactor and other parts of the complex last year under an agreement with the United States, South Korea, Japan, Russia and China.

Under the deal, North Korea has been receiving fuel aid from the five nations.

South Korean and U.S. officials welcomed the demolition of the cooling tower as an encouraging sign of North Korea's commitment to a broader deal under which Washington hopes to eradicate all nuclear assets of the communist country.

In response to North Korea's actions US president George Bush said Washington would start the process of taking Pyongyang off its list of state sponsors of terrorism.