Manila  - The Philippine military said Thursday that it was pulling back troops away from Muslim militants holding captive three international Red Cross staff on a southern island after the kidnappers threatened to behead one of the hostages.

A leader of the Muslim Abu Sayyaf rebels also promised to a Philippine Red Cross official to free one of the hostages if government forces move away from their encampment in Indanan town on Jolo island, 1,000 kilometres south of Manila.

Brigadier General Gaudencio Pangilinan, the military's civil relations chief, said the repositioning of troops would give way to negotiations.

"We will return to our former position to give way to negotiations," he said while declining to give details on the troop movement.

The International Committee of the Red Cross said a leader of the Abu Sayyaf rebels made "direct threats" against their hostages - Swiss Andreas Notter, Italian Eugenio Vagni and Filipino Mary Jean Lacaba - after fighting Monday and Tuesday.

Three Marines were killed and 19 wounded in the clashes, the military said. Authorities said six Abu Sayyaf rebels were also killed and several guerrillas wounded, including commander Albader Parad.

The threat against the hostages was aired over Manila radio station dzEC by a man claiming to be Parad.

"If the military operation gets closer to us and fighting ensues, I will cut off the head of one of them," the man told dzEC. "What I will say will happen."

The committee said it was "extremely worried about the three persons' safety" after the threat.

Senator Richard Gordon, chairman of the Philippine National Red Cross, said he talked with Parad Wednesday night and reached a "gentlemen's agreement" to free one of the hostages once the military pulls back.

"It was a good thing that Parad agreed in the end that if the military pulls out, they will give us one [of the hostages]," he said.

The hostages were abducted January 15 after visiting the Jolo provincial jail to oversee a water and sanitation project.

The Abu Sayyaf has been blamed for some of the worst terrorist attacks and high-profile kidnappings in the Philippines. In the past, the rebels have beheaded hostages, such as an American tourist in 2001, when the government refused to give in to their demands. (dpa)