Libya's internationally recognised government has urged Lebanon to release Hannibal Qaddafi from custody, after a video was released showing the son of former Libyan leader Muammar Qaddafi complaining about his conditions in what appeared to be an underground cell.

Mr Qaddafi has been held in Lebanese custody since 2015 and was taken to hospital three times last year during a hunger strike in protest at his situation.

Lebanon has accused him of concealing information about the fate of Imam Musa Al Sadr, a revered Lebanese Shiite cleric who disappeared while on a trip to Libya in 1978.

Mr Qaddafi, who was two years old at the time, maintains his innocence and says he is a victim of injustice.

Libya's Ministry of Justice said Mr Qaddafi must be released “unconditionally” and that there was not “the slightest evidence linking him to the case for which he is detained”.

The ministry said it hoped to receive an official response from Lebanon that his conditions had improved.

In footage released by the Lebanese media outlet Al Jadeed over the weekend, Mr Qaddafi says, “I’m living in humiliation. I’m a political prisoner, and my case is related to a file I know nothing about.

“My father informed me that Imam Musa Al Sadr left Libya for Rome, and there he disappeared.”

Mr Qaddafi fled Libya in 2011, amid the revolution against his father's 42-year rule. Muammar Qaddafi would be killed by rebel fighters in the Libyan city of Sirte.

He had been living in exile in Syria with his Lebanese wife, Aline Skaf, and children when he was abducted and brought to Lebanon.

He was later handed over to Lebanese authorities by a local armed group.

Earlier this year, international non-governmental organisation Human Rights Watch said Mr Qaddafi was being held “in pretrial detention on spurious charges”.

Lebanese authorities “have released little information on his judicial status and the legal basis for his ongoing detention”, the rights group said.

Last year, Libya's attorney general Siddiq Al Sour sent a request to his Lebanese counterpart asking why Mr Qaddafi was being held and asked that he be either handed over to Libya or allowed to return to Syria.

Mr Al Sadr founded the Amal Movement, which – along with Iran-backed Hezbollah – dominates Shiite Muslim politics in Lebanon.

Amal is led by long-time Lebanese Parliamentary speaker Nabih Berri.