Indian authorities have seized an arms-laden ship operated by a US-based security firm after the on-board crew failed to produce valid documents for their weapons.

Officials said the vessel entered Indian waters without authorisation and was carrying a significant number of semi-automatic weapons, which is unusual for such ships raising concerns of Indian authorities.

The ship has been detained and all its 10 crew members and 25 armed guards are being interrogated. Those on board are said to include British, Estonian, Ukrainian and Indian nationals.

According to local reports, the vessel's captain told Indian authorities that AdvanFort, the maritime security company, provides armed escorts to cargo ships in piracy-prone regions.

It is not uncommon in the southern Indian Ocean and in the Gulf of Aden for merchant ships to be accompanied by armed ships to deter pirates.

"At the moment the documents are still awaited. We have to see how valid are the documents that they do produce towards their entry into Indian waters and carrying arms and ammunitions," Coast Guard Commandant Anand Kumar told Reuters.

The ship, registered in Sierra Leone, West Africa, was seized in the Indian port of Tuticorin, the southern tip of India. The US consulate in the southern Indian city of Chennai has not responded to the incident.

In February 2012, two Italian marines were arrested by Indian officials for shooting dead two Indian fishermen in the same waters sparking a major diplomatic row between the two countries. The marines, facing charges in India, did not return to the country after they were allowed to travel to Italy for elections.