Suspected Muslim rebels have kidnapped three representatives of the Geneva-based International Committee of the Red Cross in the southern part of the Philippines.
They include a Swiss, an Italian and a Philippine national.
An armed group abducted them as they were travelling in an ICRC vehicle on the southern island of Jolo, Richard Gordon, the head of the Philippine National Red Cross Society said on Thursday.
The alarm was raised when the workers failed to arrive for a flight to the mainland.
A military spokeswoman said troops had recovered the ICRC vehicle and were told by locals that the gunmen were taking the captives toward the mountainous interior of the island. Police said they were in a "hot pursuit operation".
Officials believe the Muslim rebel group Abu Sayyaf is responsible. The group is notorious for kidnappings and is based on Jolo.
"I am appealing to the Abu Sayyaf to free those people, because they are neutral in any conflict. They do not realise this but these people help them if they get wounded and get them out of the conflict areas," Gordon said.
The Swiss foreign ministry said it was "very concerned" for the well-being of the captives, and would do everything possible to enable them to be freed quickly and without any conditions.