New Delhi: Terming the incident of killing of fishermen in Kerala by security guards of an Italian ship as "serious and unfortunate", Defence Minister A K Antony on Thursday said investigation is on and law will take its own course in the matter.

"It is very serious and unfortunate incident," he told reporters on sidelines of a function here at the South Block.

Underlining that strict vigil is maintained by the authorities, Antony said, "Kerala police and Coast Guard officers are visiting the people concerned...we want everything as per law. At this stage, saying too much is not correct. But I can tell you law will take its own course."

The Defence Minister was interacting with media persons after distributing trophies to the IAF and BSF marching contingents at the Republic Day Parade. The two teams were adjudged the best marching contingents at the event.

On Wednesday night off the Kollam coast, two fishermen in a boat were killed after guards on board an Italian merchant vessel fired at them, suspecting them to be pirates.

Official sources said there were 11 fishermen in the boat at the time of the incident. Of them nine were sleeping and the driver and another person who were awake were shot dead.

"There was no prior warning as reported by the crew," a source said, adding that the matter was now being investigated by the Navy, Coast Guard and local police.