US Secretary of State Condoleezza Rice said that North Korea still had much work to do despite going ahead with long-delayed steps in the six-nation disarmament process.

"We know North Korea has a record of not living up to its obligations. So we are going to monitor very carefully," Rice said after meeting fellow ministers in the ancient Japanese capital of Kyoto.

"In order for North Korea to re-enter in some way the international community of states, it will have to deal with many issues, including human rights issues," Rice told reporters.

The G8 -- Britain, Canada, France, Germany, Italy, Japan, Russia and the United States -- met in Kyoto as North Korea blew up a cooling tower in a symbolic step to show its commitment to denuclearisation.

The televised explosion came a day after North Korea delivered a declaration of its nuclear programmes including details of its plutonium, which it used to test an atom bomb in 2006.

The declaration was made nearly seven months late amid US allegations that North Korea sold nuclear technology abroad and ran a secret uranium enrichment programme in addition to its declared plutonium.

The United States still has "serious questions about highly enriched uranium programmes in North Korea as well as proliferation activities," Rice said. "So there is a long road ahead."

G8 ministers said here in a statement the goal should be "abandonment of all nuclear weapons and existing nuclear programmes by North Korea."

The G8 also took up a key concern of host Japan -- resolving a row over North Korea's kidnappings of Japanese civilians in the 1970s and 1980s to train its spies.

The ministers "strongly urge North Korea to take prompt action to address other security and human rights/humanitarian concerns including the early resolution of the abduction issue," the statement said.

North Korea returned five abductees in 2002 and said the case was closed. But in a reversal under US pressure, North Korea agreed this month to reinvestigate the fate of the kidnap victims.

Japan had opposed a US decision Thursday to remove North Korea off its list of state sponsors of terrorism due to the kidnapping row.

North Korea welcomed the decision, which paves the way for the impoverished state to receive US aid and international loans.

But Rice said that the United States still had numerous sanctions on North Korea that it could use as pressure on the abduction row.

"The United States retains -- very much -- plenty of leverage to deal with North Korea going forward," Rice told reporters after talks on the sidelines with Japanese Foreign Minister Masahiko Komura.

"This is a terrible, terrible thing that North Korea did," Rice said of the abductions. "They must be accountable for it and they must resolve the issue."

Komura said he was encouraged by fellow G8 ministers' expression of support on the sensitive abduction issue.

"Neither Secretary Rice nor I are thinking about pleasing North Korea by worsening Japan-US relations," he said.