Khamis Gaddafi, youngest son of the former Libyan dictator, has allegedly been killed during fighting in the town of Bani Walid, a year to the day that rebel forces killed his father, Muammar.

A short statement from the Libyan national congress spokesman, Omar Hamdan, said the 28-year-old was killed "in battle" but gave no further details. His body was apparently found after a day of heavy fighting between the town's pro-Gaddafi garrison and militias allied to the Libyan government. Government forces reported 13 dead and 121 wounded, amid a fourth day of bitter clashes for control of the town.

Khamis's alleged killing prompted wild celebrations in Misrata, Libya's third city, which was besieged for six months by his 32nd Brigade, blamed for an orgy of murder, rape and torture.

Khamis, who has been reported dead several times before, was known as one of the most hardline of Gaddafi's sons: after studying in a Russian military academy, he formed the 32nd Brigade as a special unit to be at the service of his father.

Reports said his body was being brought to Misrata, in a repeat of last October when his father's body was put on public display before being buried at a secret site. Khamis has been wrongly reported dead several times.

For many Misratans, the unconfirmed death of their chief tormentor was a cause for both celebration and torment. Former militiaman Muhsen al-Gubbi, who battled with Khamis's forces in the city last year, said: "I want to cry. I am still waiting to see his body, I want to make sure he is dead."

Earlier in the day another leading member of Gaddafi's administration, former spokesman and foreign minister Moussa Ibrahim, was captured as he tried to flee north of Bani Walid. But further confusion emerged after an audio clip posted on Facebook purporting to be the voice of Moussa Ibrahim denied his capture. There was no independent verification of the authenticity or timing of the post.

Khamis never married, and was regarded as on the side of his older brother Moatasen, forming the "muscle" of the Gaddafi family, in contrast to Saif Al Islam, now in jail in Libya on war crimes charges, who until last year's revolution portrayed himself as a political reformer.

The presence of two such senior figures from the old order appears to confirm assertions by Libyan officials that Bani Walid had become a safe haven for former Gaddafi officials. "A lot of people who supported Gaddafi are hiding now in Bani Walid, we have a list of names," said Libyan army spokesman Mohammed El Gandus.

The rest of Muammar Gaddafi's clan is scattered. Wife Safiya is in Algeria, with eldest son Muhammad, fifth son Hannibal and their only daughter by birth, Aisha. Saadi Gaddafi has sought refuge in Niger, which refused bids to extradite him, while Saif is in custody. The whereabouts of the Colonel's adopted daughter, Hana, is unknown.