Italian police providing security for this week's G7 summit were being given new accommodation on Tuesday after having been "packed like mice" onto a rundown cruise ship, their union said.

Whereas Italian Prime Minister Giorgia Meloni, US President Joe Biden and the other Group of Seven leaders will sleep at a luxurious five-star resort during the summit in Puglia, some 2,600 police officers working at the event were given more second-rate accommodation.

The regional SILF union representing Italy's financial police on Monday complained that its officers had been sleeping on the insalubrious "Mykonos Magic" cruise ship in the port of Brindisi or even in vans, writing on Facebook that they were "packed like mice" inside.

"Many police, after long hours of travel, were forced to sleep in precarious conditions on a cruise ship or in cramped vans due to lack of rooms," wrote the union.

According to La Repubblica daily, the ship's broken air conditioners meant the officers had to sleep with their cabin doors open as temperatures topped 30 degrees Celsius, while water dripped from ceilings.

Police were also forced to wait in long queues to be fed cold meals, the newspaper said.

The national SILF union later announced that the general command of the financial police had begun reallocating the officers to more "dignified structures".

Police and soldiers across Italy have been deployed to Puglia for the June 13-15 summit, being held at the five-star Borgo Egnazia resort between Bari and Brindisi on the Adriatic coast.