Muammar Gaddafi is thought to be hiding near the town of Ghadamis near Libya's border with Algeria, a senior Libyan military official told the Reuters news agency.
Hisham Buhagiar, who is part of Libya's new leadership and coordinator of the hunt for Gaddafi, told Reuters that the deposed Libyan leader was believed to have been in the southern town of Samnu last week before traveling to Ghadamis.
"One tribe, the Touareg, is still supporting him and he is believed to be in the Ghadamis area in the south," Buhagiar told Reuters.
He said Gaddafi's son Saif al-Islam was in Bani Walid and another son, Mutassem, was in Sirte, the family's hometown and the site of a continuing intense battle for control between rebels and Gaddafi loyalists.
Buhagiar told Reuters that Gaddafi's sons may yet decide to flee Libya for Niger.
International officials and aid agencies have expressed fears for the more than 200,000 civilians caught up in heavy fighting in Sirte and Bani Walid, the BBC reports.