The Abu Sayyaf rebel group has chosen a new leader, a senior general in the Philippine army has said.
Philippine troops are trying to hunt down insurgents in Jolo
Lieutenant General Romeo Tolentino said Yasser Igasan was chosen to head the militants at a meeting of commanders two or three weeks ago.
However, other military figures say they are still trying to confirm the appointment.
Abu Sayyaf is the smallest of four Muslim rebel groups in the Philippines, with about 400 members.
It is blamed for kidnappings and bombings, including an attack on a ferry in 2004 that killed more than 100 people.
Lt Gen Tolentino said Mr Igasan was among the group's founders. He is thought to have studied in the Middle East in the mid-1990s.
A senior police officer told the Reuters news agency that Mr Isagan lacked military training, and could become the group's spiritual leader, while a more experienced commander could take over the military side.
The US has listed Abu Sayyaf as a terrorist organisation and says it has links to al-Qaeda.
Former leader Khadaffy Janjalani and senior figure Abu Sulaiman, were killed by Philippine troops in September and January.
The Philippine authorities have been trying to flush Abu Sayyaf rebels from hideouts in Jolo, backed by US military surveillance and other non-combat assistance.
Meanwhile, Human Rights Watch has accused the Philippine military of carrying out the extra-judicial killing of hundreds of left-wing activists and journalists in recent years.
The report by the US-based group described the military action as a "dirty war" and called on the Philippine authorities to take responsibility for their failure to prosecute anyone for the killings.
Local rights groups say more than 800 activists have disappeared or been killed since 2001.
The government says most of the victims died in fighting with the military or were killed during internal communist purges.