More than 60 people were reported missing after the boat sank near southern Italy's Calabria region in mid-June, with 11 people rescued.

According to non-governmental organisations and accounts from victims' families, the boat was carrying mostly Kurdish migrants from Iraq and Iran, along with Afghan families.

"Four people considered to be leaders in human trafficking were arrested," the Asayish, security forces the northern Iraqi autonomous region, said in a statement.

They gave only the initials of the four "suspected of being involved in the illegal travel of residents of the Kurdistan region to the Italian coast, which led to the sinking of their yacht".

The four were arrested in the province of Sulaimaniyah, a security official told AFP, requesting anonymity.

So far 36 bodies have been recovered by the authorities in Italy, according to the latest report on Tuesday, with ongoing efforts to locate those still missing from the boat that departed Turkey.

In mid-May, Kurdistan authorities announced the arrest of a migrant smuggler nicknamed "Scorpion", wanted in several European countries.

The International Organization for Migration says about 3,155 migrants died or went missing in the Mediterranean last year and more than 1,000 people have died or gone missing so far this year.

The central Mediterranean migration route, on which Italy lies, is the deadliest in the world and represents 80 percent of the deaths on that sea.

Thousands of migrants depart from Libya and Tunisia by boat towards Europe, with Italy often the first landing point.