The experts, from the United States, Russia and China, were expected to meet North Korean officials Friday to discuss the measures required to shut down the complex, the Xinhua news agency said in a report from Pyongyang.

Their main task is to decide the most effective way of permanently shutting down the plants at the Yongbyon complex, which Pyongyang closed in July as part of a February multilateral agreement.

The experts refused to comment on their trip, Xinhua said, but the US said Wednesday that North Korea had given them full access.

After over four years of stalemate, the North agreed on February 13 under the six-party framework to declare and disable its nuclear program in return for aid, security guarantees and major diplomatic benefits.

In July it shut down its only operating reactor at Yongbyon in return for 50,000 tonnes of fuel oil.

The International Atomic Energy Agency in August confirmed the shutdown, along with the closure of a nuclear fuel fabrication plant, a reprocessing plant and a separate 50-megawatt reactor, only partly built, at Yongbyon.