Human Rights Watch called on Lebanon Tuesday to release a son of Libya's former leader Moammar Gadhafi, saying he had been held on "spurious charges" for eight years.

Lebanon in 2015 arrested and accused Hannibal Gadhafi, known for living the high life, of withholding information about the disappearance of Lebanese Shiite cleric Imam Moussa Sadr in 1978.

But HRW said that he was only two at the time the cleric disappeared, and accused Lebanon of subjecting him to an "apparent arbitrary detention on spurious charges."

"Spending eight years in pre-trial detention makes a mockery of Lebanon's already strained judicial system," the group's Hanan Salah said in a statement.

Sadr -- the founder of the AMAL Movement, now a main ally of Hezbollah -- went missing during an official visit to Libya, along with an aide and a journalist.

Lebanon blamed the disappearances on long-time Libyan strongman Moammar Gadhafi -- overthrown and killed in a 2011 uprising -- and ties between the two countries have been strained ever since.

"It's understandable that people want to know what happened to Imam Sadr," Salah said. "But it is unlawful to hold someone in pre-trial detention for many years merely for their possible association with the person responsible for wrongdoing."

In June 2023, a judicial official had told AFP that the case of Hannibal Gadhafi had been halted as they awaited information from Libyan authorities.

In August that year, Lebanon received a letter from Libyan authorities demanding Gadhafi's release, but a judicial source told AFP that he would not be freed before Tripoli revealed information about Sadr's disappearance.

Later that month, Parliament Speaker and Amal Movement chief Nabih Berri accused Libya of "failing to cooperate" with the Lebanese judiciary and "concealing" information about the case.