A UN team is to arrive in Libyan capital Tripoli to investigate allegations of human rights abuse since the start of the conflict, the BBC reports.
The Libyan government has said it will co-operate with the probe.
The UN investigators say they will look at all alleged violations, including those the government claims have been committed by rebels or NATO forces.
Obama orders $25 million in aid to Libyan rebels
US President Barack Obama has formally ordered a drawdown of $US25 million ($A23.17 million) in urgent, non-lethal American aid to Libyan rebels fighting Muammar Gaddafi.
The grant of funds to Libya's Transitional National Council, which had been signalled last week, was contained in a memo from the president to Defence Secretary Robert Gates and Secretary of State Hillary Clinton.
Officials said last week that the aid could include vehicles, fuel trucks, ambulances, medical equipment, protective vests, binoculars, and radios.
The formal granting of US aid came on a day when British Defence Secretary Liam Fox said in Washington that Libya's rebels had gained "momentum" on the battlefield and that Gaddafi's regime was on the "back foot".
After nearly three hours of talks at the Pentagon with Gates, Fox painted an optimistic picture of the Libya conflict despite fears on both sides of the Atlantic that the war could turn into an open-ended stalemate.
A NATO spokeswoman meanwhile said that the alliance was considering sending a civilian "contact point" to Libya's eastern rebel bastion of Benghazi in order to improve political relations with the opposition.
