SEOUL - North Korea toppled the cooling tower at its nuclear plant on Friday, a South Korean broadcaster said, a move showing the North's commitment to a nuclear deal a day after submitting a list of its atomic plans.

Global powers still need to verify the claims Pyongyang made in its atomic inventory and experts say the dramatic event will leave unresolved questions about the North's declaration, such as accounting for its nuclear weaponry and proliferation.

South Korean broadcaster MBC, one of the five foreign news organisations on hand to witness the event at the Yongbyon nuclear plant, said the tower was brought down in the afternoon and it would soon transmit video footage of the event.

Steam coming from the tower in spy satellite photographs has been the most visible sign of operations at the facility, designed to produce arms-grade plutonium.

Another local broadcaster cited an unnamed, high-ranking South Korean source as saying that six-country talks on ending North Korea's nuclear arms programme could resume as early as next week.

Christopher Hill, the chief U.S. envoy to the six-way talks, said in Japan on Friday that all the parties had received a copy of the declaration and would now move to verify its contents.

U.S. President George W. Bush on Thursday cautiously welcomed the declaration but warned North Korea, which tested a nuclear device in October 2006, that it faced "consequences" if it did not fully disclose its operations and continue to dismantle its nuclear programmes.

Responding to an unusual opening by the secretive communist state, Bush took a step towards removing North Korea from a U.S. list of state sponsors of terrorism and issued a proclamation lifting some sanctions under the Trading with the Enemy Act.