Manila  - Muslim militants abandoned a lending firm employee held captive for four months in the southern Philippines after government troops launched an offensive and killed three rebels, the military said Sunday.

Captain Neil Estrella, a military spokesman, said Lea Patris was left by Muslim Abu Sayyaf rebels as they fled the attack late Saturday in Tipo-Tipo town in Basilan province, 900 kilometres south of Manila.

"We launched an operation on Saturday and we killed three rebels," he said. "The hostage was abandoned as the rebels fled the attack. There were several enemies wounded but they were brought by their comrades."

Patris was abducted by the Abu Sayyaf with another co-worker in nearby Sumisip town on February 3. Her co-worker was freed three days later.

The offensive against the Abu Sayyaf was launched days after the rebels released Sri Lankan peace advocate Umar Jaleel on Wednesday following negotiations.

Jaleel, a volunteer with the Brussels-based Nonviolent Peaceforce, was seized by the group on February 13.

Rear Admiral Alex Pama, a regional navy commander, said government forces had already penetrated the Abu Sayyaf lair on Saturday.

"But the rebels fled like cowards so we only got three of them," he said. "In the confusion, they left Lea Patris, who took the opportunity to escape."

Estrella said there was no sign of three public school teachers who were still reportedly being held captive by the rebels.

"We are still looking for them," he said.

The Abu Sayyaf is the most notorious Muslim rebel group in the southern Philippines. It has been blamed for some of the worst terrorist attacks and high-profile kidnappings in the country.

Abu Sayyaf rebels are also holding captive an Italian Red Cross worker in the nearby island of Jolo. Eugenio Vagni, 62, has been in captivity since January 15. His two co-workers who were abducted with him were freed in April.