Italian police say some of the nearly 370 migrants who survived the capsizing of a fishing boat told investigators that about 200 people likely perished because smugglers kept them inside the hold.

A day after survivors arrived in Sicily aboard an Irish naval vessel which docked in Palermo, police on Friday said migrant accounts helped confirm preliminary estimates by rescuers that some 600 were on the 20-meter-long fishing boat.

The police now estimate that 650 migrants were aboard when the boat capsized on Wednesday off Libya's coast as rescuers approached.

The police say some of the five smugglers, who were detained on Thursday when they disembarked with survivors, were tasked with using violence if necessary to ensure the migrants didn't move.

Twenty-six bodies have been recovered.