New Delhi: Defence Minister A.K. Antony on Friday called for "punishing" the "guilty" crew of an Italian cargo ship who shot dead two Indian fishermen in the Arabian Sea off the Kerala coast on Wednesday.

Investigations into the killing of the two fishermen was in progress and what had happened was against the law and the norms of shipping, Antony told reporters here on the sides of an Indian Air Force event.

"Investigation is going on...and they (Kerala Police) are questioning all those people involved with the assistance of the Indian Coast Guard.

"At this stage giving more information is inappropriate on my part. At the same time, I can tell you we take this issue seriously. It is unfortunate," he said.

"What happened was against the law, against all norms. So, the guilty will have to be punished," Antony said, noting that the law will take its own course.

India had Thursday summoned the Italian envoy and protested over the shooting of two Indian fishermen by security personnel of an Italian cargo vessel. Italy was also asked to cooperate with the Kerala Police.

The incident triggered a diplomatic row, with Italy differing from India's description of the events. Italy said its naval personnel on board the Enrica Lexie first fired warning shots after they were allegedly attacked in international waters by people on an Indian fishing vessel.