A UN team is due to arrive in Tripoli to investigate allegations of human rights violations in Libya since the start of the conflict in February, the BBC reported Wednesday.
The team was appointed by the UN Human Rights Council following the Libyan government's crackdown on protesters.
The government has said it will co-operate with the inquiry.
The three investigators say they will look at all alleged abuses, including those the government says have been committed by rebels or Nato forces.
Separately, the UN Security Council has asked the International Criminal Court to investigate Libya on possible charges of war crimes.