The International Criminal Court says Libya has not responded to a request for information about the health and status of Saif al-Islam Gaddafi before a deadline which expires on Tuesday. The former Libyan leader's son was captured in southern Libya in November. The ICC, based in The Hague, has indicted him for crimes against humanity and wants to know officially whether Libya plans to hand him over. It could refer Libya to the UN Security Council if it does not respond. Colonel Gaddafi's most prominent son is being held in the western town of Zintan. He was arrested while trying to flee the country. Saif al-Islam Gaddafi told a representative of Human Rights Watch last month that he was being treated well, but had not seen a lawyer or the detailed charges against him. Fred Abrahams of Human Rights Watch told the BBC that he had the impression from their meeting that Saif al-Islam "doesn't fully understand that he is no longer one of the most powerful people in the country". The BBC's Gabriel Gatehouse, who is in Tripoli, says the case of the former dictator's son charged with war crimes is becoming an unlikely cause for human rights campaigners.