Unusual activity has been spotted around the Yongbyon reactor, which produces the raw material for plutonium to make nuclear weapons, parliament's intelligence committee said in a statement.

The National Intelligence Service (NIS) said the statement was based on its own report to parliament earlier Thursday.

The report raises hope the North may be preparing to take the first step under a six-nation February disarmament pact, after an April 14 deadline for action lapsed due to a dispute over the North's frozen bank accounts in Macau.

"A new small building, which is believed to be (accommodation) facilities, was constructed behind a reactor at Yongbyon in March and April, along with repair work on its slip road," the parliamentary committee said.

"Signs of rolling the land have been detected around a facility for the storage of nuclear waste since mid-March," it said.

"We believe such activities are part of preparations for the stay of IAEA (International Atomic Energy Agency) inspectors."

A NIS spokesman told AFP that this was also the spy agency's conclusion.

News reports last week said unusual people and vehicle movements had been spotted around the cooling tower and parking lot at Yongbyon. The NIS confirmed the movements but said at the time it did not know whether these indicated a planned shutdown.

Chun Young-Woo, South Korea's envoy to the six-party negotiations, earlier also raised hopes of progress, saying the dispute over the Banco Delta Asia (BDA) accounts would be settled soon.

In the pact the North agreed to disable its nuclear programmes in exchange for one million tons of fuel oil or equivalent aid as well as security and diplomatic benefits.

Under the first phase, it was supposed to have sealed Yongbyon by April 14 in the presence of UN inspectors.

But the communist state, which tested a nuclear bomb last October, said it would only make a start after it receives the 25 million dollars frozen at BDA at US instigation on suspicion of money-laundering and counterfeiting.

Macau's financial authorities have unblocked the funds and the United States has said they are available for collection.

The North has confirmed that problems in transferring its cash are delaying settlement of the dispute. Analysts say other foreign banks are reluctant to accept the transfers because the money is seen as tainted.

"Talks between related parties are proceeding well and a way to resolve the BDA issue will be found sometime next week," Chun told reporters on his return from a visit to the United States.

"North Korea is also making earnest endeavours and hectic talks are now under way among related parties."

Chun met his US counterpart Christopher Hill, Deputy National Security Adviser Jack Crouch and other officials in Washington.

South Korea's Foreign Minister Song Min-Soon has said that apart from just recovering the money from BDA, North Korea wants to ensure that its access to the international financial system has been restored.