Police in the southern Indian port city of Tuticorin have arrested the crew of a US-owned ship on charges of illegally transporting weapons and ammunition in Indian waters.

Eight crew members and 25 security guards aboard the MV Seaman Guard Ohio were arrested on Friday after they failed to produce documents allowing them to carry the weapons, said India's foreign secretary, Sujata Singh.

The men, from India, the UK, Estonia and Ukraine, were charged with illegal possession of weapons and ammunition, and entering India's territorial waters without permission, said Singh.

The crew and security guards are co-operating with the investigators Sujata Singh, Foreign Secretary

"The crew and security guards are co-operating with investigators," she said, adding that information about the case had been shared with representatives from the US embassy in New Delhi.

Police said that they had seized 35 automatic weapons and nearly 5,700 rounds of ammunition from the security guards on the ship.

Two of the crew members were not arrested and were allowed to stay on board to carry out maintenance.

The ship is owned by the Virginia-based security company, AdvanFort, but is registered in Sierra Leone. It was detained on October 12 and has been in Tuticorin port in Tamil Nadu state.

AdvanFort's president, William Watson, said: "The Indian coast guard approached us and asked us to follow them into the port. We would never have entered Indian waters otherwise."

The ship's captain told investigators that the company provided armed escorts to merchant vessels travelling in areas of the Indian Ocean prone to piracy.

India is currently sensitive about the presence of armed security guards on merchant ships after two Italian marines shot dead two fishermen last year, after mistaking them for pirates. The marines are facing trial in India for the deaths.