Jolo Island, southern Philippines is a base for the Abu Sayyaf gang
Gunmen have abducted three aid workers from Italy, Switzerland and the Philippines on southern Jolo island, the Philippine National Red Cross says.
The Red Cross chairman, Senator Richard Gordon, said the three were in a car on their way to Jolo airport.
They had been visiting a local jail when they were intercepted by armed men on motorbikes, he said.
The island is a stronghold of the Abu Sayyaf group, which is notorious for kidnappings and terror attacks.
A regional military spokeswoman has identified the three aid workers from the International Committee of the Red Cross (ICRC) as Swiss Andreas Notter, Italian Eugenio Vagni and Filipino Jean Lacaba.
"They had been carrying out a water and sanitation project to improve the condition of detainees," ICRC spokesman Reynaldo Guioguio told AFP news agency.
Senator Gordon said the aid workers' driver and two other Filipinos were released and reported the incident.
Reuters new agency said that marine officials on Jolo confirmed the incident.
"I am appealing to the Abu Sayyaf to free those people, because they are neutral in any conflict," Mr Gordon said.
"They do not realise this but these people help them if they get wounded and get them out of the conflict areas," he said.
Abu Sayyaf has twice attacked luxury beach resorts and taken away tourists, including Westerners.
They have held them for months at a time and secured large ransoms for their release.
In 2001, three kidnap victims, including an American, were beheaded by their captors.
The Abu Sayyaf has also been blamed for the bombing of a ferry near Manila Bay in 2004 that killed 100 people.
Sometimes linked to al-Qaeda militants, the Abu Sayyaf group has focused on kidnaps for ransom.
The police and military say that more than 380 Abu Sayyaf fighters - down from 1,000 in 2002 - are hiding mainly in the hinterlands of predominantly Muslim Jolo and Basilan islands.
The poor and underdeveloped area is home to decades-old Muslim separatist rebellions.