The United Nations will send experts to Libya to help ensure nuclear material and chemical weapons do not fall into the wrong hands, Secretary-General Ban Ki-moon said on Wednesday on his first visit to Tripoli since the fall of Muammar Gaddafi.

Ban also offered technical support in the transition to democracy and called on the new authorities to ensure that perpetrators of human rights abuses are punished.

The former regime under Gaddafi has reported to the relevant United Nations organisations on nuclear materials, as well as chemical weapons, Ban told reporters during an afternoon visit to the coastal capital.

He said he had raised the issues with Libya's National Transitional Council (NTC) so that these materials will be securely controlled. It is very important that all these materials, very carefully and without fail, be secured.

Experts from the Organisation for the Prohibition of Chemical Weapons and the U.N.'s International Atomic Energy Agency would visit Libya, Ban added.

Gaddafi publicly renounced Libya's nuclear and chemical weapons programmes in the last decade as part of a move to restore ties with the United States, Britain and other Western states. But Libya still had nuclear material for research purposes and may have had chemical weapons stockpiles.

During the war to unseat Gaddafi, conventional weapons, including shoulder-fired anti-aircraft missiles that could be used to attack civilian aircraft, went missing from Libyan arsenals. The United States and other countries have offered help tracking some of these weapons down.

NTC chairman Mustafa Abdel Jalil said that once some of the country's frozen assets are released, the NTC will be able to properly contain the weapons and control armed anti-Gaddafi militias who still roam the country.

World leaders agreed to unblock $15 billion (9 billion pound) to help the new government restore vital services after Gaddafi's overthrow, but Libya's Finance Ministry said just a third of Libya's assets have been unfrozen.

UN HELP, RESPECT FOR HUMAN RIGHTS

Ban also offered U.N. help for elections, a new constitution, human rights, public security and the control of weapons.

The new Libyan leadership's rights record has come under international scrutiny because of suggestions its supporters may have carried out revenge killings.

U.N. rights monitors have said they intend to investigate the death of Gaddafi himself, who was filmed pleading with the fighters who captured him and then driven to a hospital dead.

In another incident, New York-based Human Rights Watch said 53 bodies were found in October, surrounded by spent rifle cartridges, on a grassy area at an abandoned hotel in a part of Sirte that was controlled by anti-Gaddafi fighters.

The United Nations is here to help, in every way we can, in any way you choose, Ban said.

Issue of transitional justice must be resolved with wisdom and restraint. It is important to hold perpetrators of human rights crimes to account, as well as promote national reconciliation.

(Editing by Peter Graff)