Defence lawyers at the International Criminal Court (ICC) have called on Libya to hand over Saif al-Islam Gaddafi, son of the late Libyan leader Muammar Gaddafi, saying that he has been physically attacked and kept in isolation.
Libyan authorities and the Netherlands-based court have been locked in a dispute over where Saif al-Islam should stand trial since his capture in November 2011.
Libya wants to try Saif al-Islam in a domestic court, where he could face the death penalty if found guilty, but the ICC on Wednesday said that he should be extradited to the Hague, where he would face imprisonment if convicted.
"Mr Gaddafi has been physically attacked" while being held in Libya, Xavier-Jean Keita, principal counsel at the ICC's Office of Public Counsel for the Defence, said in an emailed statement.
"He also suffers pain due to the absence of dental treatment. The Libyan authorities have failed to take any steps to remedy this pain by according Mr Gaddafi the medical and dental treatment ordered by the chamber almost a month ago."
The ICC issued a warrant for Saif al-Islam in June 2011 after prosecutors accused him and others of involvement in the killing of protesters during the revolt that eventually toppled and killed his father in October 2011.
But Libya says it is fitting that Saif al-Islam should face justice at home after he was caught last year disguised as a Bedouin tribesman in the Sahara desert.
Keita also said that Saif al-Islam has been given misleading information concerning the status of domestic investigations against him.
"Mr Gaddafi was advised that he was being investigated for trivial allegations concerning the absence of a licence for camels, and irregularities concerning fish farms, and that he would not be pursued for serious crimes, such as murder and rape, due to lack of evidence," the defence counsel said.
Keita said Saif al-Islam had been held in detention by the Libyan authorities for 139 days, without being brought before a judge, and had been unable to contact family and friends or to receive visits from them.
"Apart from visits from officials and prosecuting authorities, he has been kept in total isolation," Keita said.