DNA tests are being carried out in the Philippines on the body of a man suspected to be the leader of a militant group linked to al-Qaeda.
Troops launched an offensive against rebels on Jolo in August
Khaddafy Janjalani, head of Abu Sayyaf, is on a US terrorist list and carries a reward of $5m. He is wanted for killings, bombings and kidnappings.
The Philippine military had been led to the body, in a grave in a remote part of the southern Jolo Island.
The army believed it killed Mr Janjalani in a clash in September.
However, previous reports of his death have proved unfounded.
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.
The grave was located near the town of Patikul on Jolo, the army said.
Samples are being brought to the capital, Manila, for DNA testing. US forces in the south will do separate tests.
The Philippine army said captured rebels had led them to the grave. The captives said Mr Janjalani had been shot in the neck in an exchange with marines.
Gen Hermogenes Esperon said: "If we get confirmation that it is indeed Janjalani, this is a big point in our fight against terrorism."
Mr Janjalani is the younger brother of Abu Sayyaf founder Abdurajak Abubakar Janjalani, who was killed on the island of Basilan in 1998.
Philippine troops backed by the US began an offensive on Jolo in August this year to capture Mr Janjalani and Indonesian terrorism suspects Dulmatin and Umar Patek.
The latter two are suspected of involvement in the 2002 Bali bombings that killed 202 people.
They allegedly belong to Jemaah Islamiah, a regional Islamic network with links to al-Qaeda.