Manila - The Philippine military on Friday admitted facing difficulty in rescuing an Italian Red Cross worker held captive by Muslim militants for four months on a southern island.

Lieutenant Colonel Romeo Brawner, military spokesman, said troops were stepping up efforts to gather intelligence information on the exact location of Eugenio Vagni,
61, and his captors.

"We are requesting for the patience of the public and allow us to do our job to rescue Vagni," he said. "It's really hard."

"We are still continuing our rescue and intelligence operations because it is really important to identify where Vagni is," he added.

Vagni and two colleagues from the International Committee of the Red Cross were abducted January 15 on Jolo island, 1,000 kilometres south of Manila.

His colleagues - Swiss Andreas Notter and Filipino Mary Jean Lacaba - were freed separately by Muslim Abu Sayyaf rebels in April.

Alain Aeschlimann, the Red Cross' regional head of operations, said Vagni's family last spoke to him on May 8.

"While they were, of course, very relieved to hear his voice, they remain worried about him," he said. "Obviously, brief phone calls cannot do much to ease their pain."

Aeschlimann said the Red Cross was "extremely concerned" about Vagni's safety and well-being after being in captivity in the jungles for 120 days while suffering a hernia injury.

"We appeal to his abductors to release him at once," he said.

Vagni's captors belong to the most notorious Muslim rebel group in the Philippines, blamed for the worst terrorist attacks in the country as well as high-profile kidnappings. (dpa)