Of the list of 55 suspects most wanted by the coalition that invaded Iraq, six were executed, six were killed in combat, eight died in captivity, five are on the run, and 16 were freed by the Americans before they pulled out of the country in 2011.

Saddam's two sons -- Uday and Qusay -- were among those killed in fighting.

The remaining detainees include the dictator's defence minister, General Sultan Hashim Ahmad, sentenced to death in June 2007 but never executed.

The others are mid-level Baath party cadres who held positions in the military or government.

The latest to be detained is Abdel Baqi Abdel Karim Abdallah, a top Baath party official who was arrested in June 2015 in Kirkuk while in hiding.

All detained former regime officials are being held in Nasiriyah prison in the country's south, according to Badia Araf, a lawyer representing some of the detainees.

The conditions in detention are "very bad", the lawyer said, adding that General Ahmad's health was "deteriorating".

Araf said that with the exception of Jamal Mustafa Abdallah Sultan, the former "number two" for tribal affairs in jail since 2003 and the husband of Saddam's daughter Hala, the others have been sentenced.

Most of them have been condemned to death.

"I filed 30 release requests with the authorities, who didn't even answer me," said Araf.

"I think these prisoners will remain in detention until death without the intervention of human rights organisations, who have done nothing so far."

Five of Saddam's lieutenants are still believed to be on the run, the most famous being Ezzat al-Duri, former vice president of the dictator's Revolutionary Command Council whose death has been announced by authorities several times.

One of the former Baath party officials, Saif el-Din Mashhadani, was executed in Mosul by Islamic State group jihadists in 2014.

Saddam himself was captured near his hometown Tikrit in December 2003 and hanged in late 2006.