The Samarinda Port Authority in Indonesia has confirmed that an unidentified group has kidnapped seven Indonesian crewmen of the TB Charles boat in Philippines waters.

"We can confirm the kidnapping. We are coordinating with the police and military to follow up on the report," the Samarinda Port Authority chief Yus Kusmany told AFP on Thursday.

Kusmany said that one of the crewmen, Syaril, informed them about the kidnapping. Syaril was also on board. The authorities were in contact with him last at 10.20 am on Thursday when the boat was around Mangkaliat cape area.

The TB Charles Boat departed Samarinda on June 4 with 13 crewmen and was expected to return by June 27.

Seven crewmen were kidnapped while the other six members have been released. Now the boat is expected to reach Samarinda on Friday afternoon.

The Abu Sayyaf militants have reportedly demanded a ransom of RM20 million from PT Rusianto Bersaudara, the owner of the boat, to release the hostages. The phone call was received by Dian Megawati Ahmad, the wife of one of the kidnapped crewmen, Ismail.

Samarinda Mayor Syaharie Jaang reportedly met Rusianto Bersaudara on Thursday to follow up on this report.