Manila - Muslim militants holding captive three Red Cross workers in the southern Philippines have issued new demands for the release of one hostage, an official said Monday.

Interior Secretary Ronaldo Puno said the Abu Sayyaf rebels warned they would behead one of the hostages on Jolo island, 1,000 kilometres south of Manila, on Tuesday afternoon if their new demands were not met.

He said the kidnappers "demanded new repositionings" of government forces who already pulled back by as much as 15 kilometres from the rebel encampment in Indanan town.

"We are very disheartened by these new demands," Puno said. "It is physically impossible to remove everybody within 24 hours."

On the weekend, soldiers, policemen and militiamen pulled out from Indanan town in a bid to save the hostages, giving the rebels around 130 square kilometres to move around freely.

When the military cordon was up, the kidnappers were restricted to only about 30 square kilometres in the jungles of Indanan.

Puno said under the new demand, "no place (on Jolo) will be immune from any threat."

He urged the Abu Sayyaf to reconsider their "impossible demands" and not harm the hostages - Swiss Andreas Notter, Italian Eugenio Vagni and Filipino Mary Jean Lacaba.

"We hope this beheading will not be undertaken," he added.

The Red Cross workers were abducted on January 15 after visiting the provincial jail on Jolo to oversee a water and sanitation project.

Abu Sayyaf rebels have in the past beheaded hostages, including an American tourist abducted in 2001, when authorities failed to meet their demands.

The guerrillas have been blamed for some of the worst terrorist attacks in the Philippines, as well as other high-profile kidnappings of foreigners. (dpa)