Muslim rebels engaged in peace talks with the Philippine government said Monday they had joined the search for an Australian man kidnapped by an armed group in the troubled south of the country.

The Moro Islamic Liberation Front (MILF) has formed a tracking unit to help authorities recover Warren Rodwell, 53, who was seized from his home by gunmen believed to be Islamic militants last month, rebel spokesman Vol Al-Haq said.

"We are working on it and all (the information) we gather, we will feed to the ad hoc joint action group," al-Haq told AFP.

He said the MILF was working to check unverified reports that Rodwell was in the hands of the smaller Al Qaeda-linked Abu Sayyaf group in their southern island territory of Basilan.

Rodwell, who is married to a Filipina, had been living in the southern coastal town of Ipil for eight months prior to his abduction on December 5.

Authorities had imposed a news blackout on the search, although various sources had said his abductors likely took him across to Basilan, a stronghold of the Abu Sayyaf.

Local press, citing police sources, have reported that Rodwell's abductors sent his wife photographs to prove he was alive and demanded an initial ransom of one million pesos (about $23,000).

Philippine police declined to comment on the reports when contacted by AFP in Manila, as did the Australian foreign ministry.

"It would be unhelpful to comment in detail on developments in the investigation," a spokeswoman at Australia's foreign office in Canberra said.

"(Foreign officials and police) are in close contact with Mr Rodwell’s family and are keeping them informed of developments throughout this difficult ordeal," she added.

The Abu Sayyaf is a small band of Islamic militants which was formed with seed money from Al-Qaeda in the 1990s.

It has carried out numerous kidnappings for ransom, often targeting foreigners and Christians and a spate of high profile bombings over the past two decades.

It is not included in the peace talks between Manila and the 12,000-strong MILF, which had agreed to help government forces go after criminal gangs and terrorists in areas where it operates.