Italian victims 'tortured in Dhaka attack': source

Nine Italians who died in the Bangladesh hostage crisis last week were tortured by the Islamist militants before they died, a source says.

Ciampino airport return of the victims to Dhaka in Bangladesh. Source: AAP

Islamist militants tortured a group of Italians before killing them during an attack on a restaurant in the Bangladeshi capital of Dhaka last week, a legal source says.

The bodies of the nine Italians, most of whom worked in the clothing industry, were flown back to Rome on Tuesday.

Autopsies showed that many of them had been slashed with knives and had suffered slow deaths, and some had been mutilated, the source said.

In all, 20 people died in the Dhaka assault, which started late on Friday night.

The victims, mostly foreigners, included Japanese, Indians and Americans as well as the Italians .

Islamic State said it was responsible for one of the most brazen attacks in Bangladesh's history, posting pictures of the five men they said took part in the onslaught.

Officials said most of the militants had attended prestigious schools or universities in Dhaka and Malaysia.

One was the son of a politician.

The Holey Artisan restaurant in Dhaka where the attack took place is popular with foreigners, and investigators in Rome are looking into whether Italians were specifically targeted, a judicial source said.