(AP Photo)

NEW DELHI - Indian police on Sunday detained two Italian marine security guards for allegedly shooting to death two Indian fishermen they mistook for pirates.

The suspects were brought ashore in southern India and placed in custody for further questioning, police said.

The two Italians were part of a six-member security team on the cargo ship the Enrica Lexie, and are suspected of firing Wednesday on an Indian fishing boat they mistook for a pirate ship off Kerala state. Two fishermen were killed instantly.

Italy's ambassador to India and a delegation of experts from Italy's foreign, defence and justice ministries arrived in the capital Sunday and discussed the case with Indian officials, the Italian foreign ministry said in a statement.

The Italian government maintains the case should be handled by its own judicial authorities "since the deeds happened in international waters on an Italian-flagged ship," the statement said.

The Italians contend that the presence of military personnel aboard the cargo ship is governed by an Italian law conforming to U.N. anti-piracy resolutions, and that such personnel are part of the Italian state and thus immune to the jurisdiction of foreign states.

The meeting failed to yield agreement, the ministry said.

Piracy has emerged as a major threat to merchant ships in the Indian Ocean and Arabian Sea, with Somalia-based pirates hijacking ships and crew for ransom.

Several countries, including India, allow ship owners to deploy armed security guards on ships.