The International Committee of the Red Cross on Saturday appealed to Islamic militants who are still believed to be holding an Italian staffer hostage to release him unharmed.
Philippine security forces on Saturday rescued another ICRC worker, Andreas Notter, who was held hostage for three months on the Indonesian island of Jolo. But his colleague, Eugenio Vagni, who was kidnapped at the same time, was still believed to be captive.
"We are, of course, very relieved that Andreas will soon be back in the arms of his loved ones," Alain Aeschlimann, the ICRC's head of operations for South-East Asia and the Pacific, said in a statement.
"But we remain very concerned about Eugenio's safety and we call on the abductors to let him go safely, immediately and unconditionally."
The Indonesian government said it had no immediate details about the fate of 62-year-old Vagni, who was believed to be unwell and in need of hernia surgery.
Notter and Vagni, along with a local colleague, were kidnapped by the Abu Sayyaf group on January 15 as they left a prison on Jolo. The Filipina, Mary Jean Lacaba, was released on April 2.