Mounting the pressure on New Delhi, the Italian Embassy has sent a letter to the Union Ministry of External Affairs demanding the release of the detained Italian marines following a rogue firing off the southern coast of India, which resulted in the death of two Indian fishermen on board a fishing boat.

The incident, which led to a diplomatic fallout between the two nations, has drawn the attention of the European Union which has expressed willingness to intervene in the procedures related to the judicial trial of the detained marines.

In the letter, a copy of which was obtained by the Indian Express, Italy has yet again asked for the release of the marines who claim to have acted out of fear of being chased by a pirate boat.

Asserting that the marines enjoy jurisdictional immunity for acts committed in the exercise of their official functions, the letter said investigations by Italy's civilian and military authorities had already been initiated against the alleged perpetrators.

The Italian Navy Military Detachment that operated in international waters on board of the vessel Enrica Lexie must be considered as an organ of the Italian state, the Embassy wrote.

The conduct by the marines has been carried out in the fulfillment of their official duties in accordance with national regulations (Italian Act nr.107/2011) and orders, as well as the pertinent rules on piracy contained in the 1982 UN Convention on the Law of the Sea and in the relevant UN Security Council Resolutions on the Piracy off the Horn of Africa, the letter said.

However, Indian Premier Manmohan Singh remained unmoved by Italy's coercive tactics. Following a telephone conversation with his Italian counterpart Mario Monti last week, Singh said his government could in no way intervene in the legal proceedings involving two Indian fishermen's death. Singh had reportedly told Monti that the case was before a court of law, and the executive never interferes in the functioning of the judiciary in India.

Arguing that the incident took place in international waters, Italy has questioned India's right to arrest and try the marines under Indian jurisdiction.

The Italian Embassy, however, appreciated the steps taken by the Chief Judicial Magistrate of Kollam, belonging to the southern Indian state of Kerala, with regard to the judicial custody of the marines.

Fishermen Ajesh Pink and Valentine aka Gelastine, natives of the states of Kerala and Tamil Nadu in South India, were shot dead by members of an Italian Navy Vessel Protection Detachment on board oil tanker MV Enrica Lexie on Feb. 15.