A small private plane carrying six passengers and a crew of two crashed on Sunday into a vacant, two-storey office building in a Milan suburb, killing all eight aboard.

LaPresse news agency initially quoted firefighters at the scene saying the pilot and all five passengers aboard were killed.

But later LaPresse and other media said there were eight people aboard the flight, including a boy.

Rai state TV said the passengers were believed to be French.

Firefighters tweeted that no one other than those aboard were involved in the early afternoon crash near a subway station in San Donato Milanese, a small town near Milan.

They said several cars in a nearby parking lot were set ablaze, but apparently the vehicles were unoccupied at the time.

A thick column of dark smoke rose from the crash site and was visible for kilometres.