Seaman Guard Ohio, registered in the West African country of Sierre Leone, docked in the V O Chidambaranar port since October 12, having 31 assault rifles and more than 5000 rounds of ammunition in the ship, which were confiscated by the authorities.

Police also said they found weapons and ammunition on board, which had not been properly declared. Officials say the vessel was not authorised to carry arms in Indian waters and that it never produced the necessary paperwork.

The men had been booked under two sections of the Indian Arms Act that prohibits possession of weapons without permission. A case under Passport Act and Essential Commodities Act was also registered for procuring fuel in Indian waters in an unauthorized manner.

Police also detained three locals, who were suspected to have illegally sold diesel to the ship.

Analysts say that anti-piracy measures on high-risk shipping routes are poorly regulated and India is increasingly sensitive to violations of its maritime boundaries because of the Mumbai carnage when the terrorists sneaked in by the sea.