Pressure is mounting on Libya to hand over Saif al-Islam Gaddafi, son of the late Libyan leader, to the international war crimes court after a defence lawyer said he had been physically attacked and misled over the charges against him.

The Libyan authorities and the International Criminal Court (ICC), the war crimes court based in The Hague, have been locked in a dispute over where Saif al-Islam should face trial.

Libya wants to try Muammar Gaddafi's son in a domestic court, where he would face the death penalty if found guilty, whereas the ICC on Wednesday insisted that he should be handed over to The Hague, where he would face imprisonment if convicted.

Mr. Gaddafi has been physically attacked while being held in Libya, Xavier-Jean Keïta, 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 warrants last year for the arrest of Muammar Gaddafi, Saif al-Islam, and the Libyan leader's intelligence chief, Abdullah al-Senussi, who was arrested last month in Mauritania.

Since the elder Gaddafi was killed after being captured alive by rebel fighters, competing militias have yet to lay down their arms and Western human rights organisations have accused them of carrying out numerous extra-judicial executions and other abuses, raising serious questions about the rule of law.

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 August.

But Libya says Gaddafi's British-educated son should face justice at home. He was caught last year disguised as a Bedouin tribesman in the Sahara desert, months after telling his father's opponents they would be exterminated like rats.

The defence lawyer, Keïta, 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.

But, the lawyer added, the Libyan authorities then performed a dramatic volte-face: when asked by the ICC to hand over Saif al-Islam, they told the ICC that they wanted to investigate and prosecute him in Libya for serious crimes that come under the ICC's jurisdiction.

Keïta said Saif al-Islam has been held in detention by the Libyan authorities for 139 days, without being brought before a judge, and had been unable to communicate with his family and friends or to receive visits from them.

Apart from visits from officials and prosecuting authorities, he has been kept in total isolation, Keïta said.

(Reporting by Sara Webb; Editing by Lisa Shumaker)