AUTHORITIES are checking the personal background of the 63-year-old Japanese held hostage in Sulu following contradicting documents indicating his citizenship, a military official said.

Lieutenant General Benjamin Mohammad Dolorfino, Western Mindanao Command (Wesmincom) chief, said Toshio Ito has a Philippine birth certificate under the name of Katayama Mamaito.

Updates on President Benigno Aquino III's presidency

Dolorfino said the birth certificate showed that Ito is a native of Marawi City.

Dolorfino said the birth certificate was among the documents recovered from Ito's residents in Sitio Bas, Bangkilay village, Pangutaran town, Sulu.

“The birth certificate stated that he is a native of the province,” Dolorfino added, citing Marawi City is within the political jurisdiction of Lanao del Sur province.

“Other documents also indicate that he may be a fake doctor and involved in swindling case,” Dolorfino added.

He said Ito arrived in Pangutaran six years ago and is known as “Doctor Amir”, an herbalist in the community.

Authorities also recovered Ito's passport stating that he was born on June 18, 1947 in Hiroshima, Japan.

Ito was abducted by 10 unidentified gunmen last July 16 in Sitio Bas, Bangkila village, Pangutaran.(Bong Garcia)