The breakthrough raised hopes that an international deal to convince North Korea to abandon its nuclear weapons programmes in exchange for aid was bearing fruit after years of on-again, off-again talks.

As envoys re-opened negotiations in the Chinese capital, the North said it was willing to declare and disable all its nuclear facilities by the end of the year in line with a February disarmament deal, South Korea said.

"North Korea showed its willingness to declare and disable (its nuclear facilities) within the shortest period of time, within this year, or five to six months," South Korean envoy Chun Yung-Woo told reporters.

Chun said no definitive agreement had been reached during the six-nation talks, but there was a broad consensus among the envoys about what needed to be done for North Korea to disable all of its nuclear weapons programmes.

His remarks came just hours after the head of the UN atomic watchdog said UN inspectors, who were only allowed back into the secretive North to resume their work days ago, confirmed the North had closed down its main reactor complex.

Mohammed ElBaradei, head of the International Atomic Energy Agency, said all five facilities at the Yongbyon reactor site were now offline.

"We have verified that all five nuclear facilities have been shut down and that appropriate measures have been put in place, including sealing some of these facilities," he said during a visit to Malaysia.

"We expect that in the next few weeks we will continue to apply the necessary monitoring and verification measures," he said.

Although the February deal called for the return of the UN inspectors, the team did not resume work until Saturday because North Korea insisted it would have to get hold of frozen funds and an initial shipment of fuel aid first.

It received both in recent weeks.

Under the agreement, North Korea -- which tested an atom bomb last year -- would eventually abandon all of its nuclear weapons programmes in return for a wide range of economic, diplomatic and security incentives.

No one outside of North Korea is exactly sure about the extent of the hermit nation's nuclear weapons programme.

The United States, for instance, says that North Korea has secretly been operating a highly enriched uranium programme. Highly enriched uranium is used to make nuclear bombs.

The second phase of the accord would see North Korea declare and disable all of its nuclear programmes, and US envoy Christopher Hill went into Wednesday's talks saying he wanted this to happen by the end of 2007.

The envoys -- from China, the two Koreas, the United States, Russia and Japan -- held a series of bilateral meetings on Wednesday morning, before holding a group discussion for 90 minutes in the afternoon.

Japanese chief negotiator Kenichiro Sasae also told reporters after the group meeting that North Korea had indicated it was willing to declare and disable all of its nuclear programmes.

"I have the impression that they are prepared to discuss the next step, having implemented the first step," Sasae said, but he emphasised that no definitive deal had been struck.

"There is no agreement at this point. We discussed how long it would take to do it but did not reach a conclusion."

Six-party talks were expected to resume today.