A South Korean man who was being held in captivity by a terrorist group in the Philippines was found dead due to an illness, officials said Sunday.

The man in his 70s, identified only by his surname Hong, was kidnapped in January by Abu Sayyaf while visiting his son's residence in Zamboanga Sibugay province.

"The remains of a person believed to be Hong were discovered abandoned on a street in Sulu province in the Philippines," a foreign ministry official said, requesting anonymity.

The militants appeared to dump the remains after the elderly man died from an unspecified illness, according to another ministry official, adding no wounds were found that could have caused his death.

The terrorist organization, which was known to have demanded a ransom of 500 million pesos ($10.6 million), had been in negotiations with the Philippine police for his release.

Abu Sayyaf is known to have ties to al-Qaida and is blacklisted by the United States and the Philippines. (Yonhap)