Four Indians, including three Tamilians, have been abducted by a militant group from an offshore oil facility off Harcourt port in Nigeria, according to information received by their relatives.

Ajit Kamaraj (33), K Mohandas (37) and P Vinod (32), hailing from Vadakkankulam village in Tirunelveli district, have been working with the offshore oil rig, District Collector G Prakash told PTI over phone, quoting their family sources.

They were abducted on Friday last, along with another Indian identified as Pandurang Tari from Maharashtra's Thane district.

Prakash said he had informed the Ministry for Overseas Indian Affairs and Union home ministry about the incident.

Union Minister of State for Home Radika Selvi has also been informed.

They were trying to secure their release, he added.

The parents of the persons also have sent petitions to Chief Minister M Karunanidhi, seeking help for their release.

The abductors have demanded a ransom of $50 million, Sudarshnan, brother of Kamaraj said.

Soon after receiving the information, he got in touch with the district collector.

Sudarshnan said his brother had returned to Nigeria on Thursday, after a 28 days' leave.

As the news about the abduction spread, a pall of gloom descended over the village from where many people have left for the Gulf and African countries in search of jobs.