India's coastguard has detained a ship operated by a US security company and the 35 people on board for not producing papers authorising it to carry weapons in Indian waters.

Coastguard Commandant Anand Kumar said on Sunday that the ship was stopped on Friday and was being held in the southern port of Tuticorin along with its 10 crew and 25 armed guards until the forms were submitted.

Britons, Estonians, Indians and Ukrainians are among the detainees.

The southern tip of India is close to major trading routes from Asia to Europe.

Many cargo ships now travel with armed guards to deter pirates.

Sri Lanka, close to Tuticorin, is a popular boarding point for private armed guards.

Mr Kumar said he was still waiting for the documents, which will have to be checked to see if they allow the ship to enter Indian waters with guns and ammunition.

The Sierra Leone-flagged ship Seaman Guard Ohio belongs to AdvanFort, a US firm that specialises in fighting pirates.

In February last year two Indian fishermen were allegedly shot dead by Italian marines serving as security guards on an Italian-flagged tanker off Kerala.

The marines are currently being prosecuted in India.