Andrea Cianferoni, a member of the non-government relief organization Movimondo, was abducted near the town of Kauswagan on Mindanao island on Tuesday.

His employers say the kidnappers have demanded an unspecified amount in ransom for the hostage, who is in his 50s.

The main suspects are relatives of a Moro Islamic Liberation Front (MILF) rebel leader known as "Commander Bravo," said Philippine Marines spokesman Captain Rommel Abrau.

They are led by a man who is either "a brother or a cousin of Commander Bravo," Abrau told reporters. "We have already mobilized our troops to pursue the kidnappers."

MILF spokesman Eid Kabalu denied to Agence France-Presse on Tuesday that any of their units were involved in the kidnapping.

He said the 11,000-member armed group, waging a decades-old

separatist campaign in the Muslim south, is coordinating with the government to secure the release of the hostage.

The MILF is observing a two year-old ceasefire and is expected to begin peace talks with the Philippine government within the year.

Abrau confirmed that military units in the area were coordinating with their MILF counterparts to avoid accidental clashes with the rebels as the authorities pursue the kidnappers.

Movimondo, which is funded by donations from the European Union, the Italian government, the United Nations and wealthy benefactors, engages in health care, humanitarian aid, job creation and skills training in poverty-stricken areas.

It operates in Italy as well as Africa, Latin America, the Balkans, the Middle East, and the Philippines.