Manila - Muslim militants holding captive three Red Cross workers in the southern Philippines have threatened to behead one of the hostages if government troops do not move out of their jungle hideouts by the end of the month, officials said Wednesday.

The latest threat was issued by Abu Sayyaf rebel leader Albader Parad on Monday as the military stepped up a blockade to prevent food and supplies from reaching the guerrillas in the hinterland of Indanan town on Jolo island, 1,000 kilometres south of Manila.

Abdusakur Tan, governor of Sulu province, which includes Jolo island, said Parad reiterated the threat during a telephone conversation with Vice Governor Lady Ann Sahidullah on Tuesday.

Sahidullah is a member of a crisis committee headed by Tan to resolve the hostages crisis.

"We learned from the negotiating (team) of the task force that the Abu Sayyaf has given an ultimatum of March 28 to
31," Tan said. "According to Vice Governor Sahidullah, they will behead [one of the hostages]."

The hostages - Swiss Andreas Notter, Italian Eugenio Vagni and Filipino Mary Jean Lacaba - were abducted on January 15 after visiting the Jolo provincial jail to oversee a water and sanitation project.

Last week, clashes erupted between the Abu Sayyaf and Marines circling the kidnappers, killing three government troops and six guerrillas.

Parad threatened to behead one of the hostages if the military continued its offensive or launched a rescue attempt. He also promised to free one of the Red Cross workers if the troops moved away from their encampment.

While troops re-positioned away from Indanan, the Abu Sayyaf did not release a hostage and demanded that government forces pull back further.

The armed forces, however, ruled out a larger troop pullout.

"They are asking too much because it will be like pulling out our troops from the entire island," armed forces spokesman Lieutenant Colonel Ernesto Torres said. "It is hard to rely on what they are saying."

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)