New Delhi | The Indian Coast Guard (ICG) has detained an Iranian fishing vessel with six Indian crew off the coast of Kerala, the defence ministry said on Monday.

The vessel was detained on Sunday following a swift "sea-air" coordinated operation by the ICG, it said.

The ministry said the crew alleged that the "Iranian sponsor" of the vessel ill-treated and deprived them of basic living conditions and confiscated their passports.

Initial investigation revealed that the owner of the boat was an Iranian national who had contracted the Indian fishermen from Tamil Nadu, it said.

"The Indian Coast Guard detained an Iranian fishing vessel, with six Indian crew, west of Beypore off the coast of Kerala late on May 5. The swift sea-air coordinated operation involved the ships and aircraft of the ICG," the ministry said in a statement.

"After intercepting the boat, an ICG team boarded the vessel and thoroughly investigated it to check the involvement of any anti-national activity," it said.

"Initial investigation revealed that the owner of the boat was an Iranian sponsor who had contracted these Indian fishermen from Tamil Nadu, and issued them Iranian Visas for fishing off the Iran coast," it added.

The vessel was brought to Kochi for further investigation.

"The crew alleged that the sponsor ill-treated and deprived them of basic living conditions, besides confiscating their passports. The crew said that they had decided to escape from Iran to India using the same boat," the ministry said.