European officials have honoured the dead of the Mediterranean's worst-ever migrant disaster as more would-be refugees arrived in Italy and prosecutors questioned the suspected smugglers.

Twenty-four caskets containing the only bodies recovered from the weekend capsizing that left an estimated 800 dead were laid out for an interfaith memorial service on the grounds of Malta's main hospital.

Wails from members of Malta's African community punctuated the ceremony, which included Christian and Muslim prayers.

Gozo Bishop Mario said during the service: "We mourn them, because irrespective of our creed, nationality, race, we know they are our fellow human beings."

Malta's president and prime minister, Italy's interior minister and the EU's migration commissioner attended.

"Europe is declaring war on smugglers, and the union will collaborate with international partners," EU Commissioner for Migration Dimitris Avramopoulos said after the memorial.

Only 28 people survived the capsizing of the migrant boat last weekend and 24 bodies were recovered, including that of an adolescent whose remains were placed in the lone white casket for burial.

Catania prosecutors have accused the suspected captain, Mohammad Ali Malek, 27 from Tunisia, and crew member Mahmud Bikhit, a 25-year-old Syrian, of aiding and abetting illegal immigration.

The captain is also accused of multiple counts of manslaughter, causing a shipwreck and sequestering people, given that the hull and lower deck of the boat were bolted closed, sealing the migrants in.

Meanwhile, Italy's border patrol has brought 220 migrants rescued some 40 miles off the coast of Libya to Catania, Sicily.