Italian police have seized a rundown cruise ship that was lodging officers working the G7 summit before widespread complaints prompted their transfer to hotels, a union said Wednesday.

The COISP police union published a statement Wednesday saying the "Mykonos Magic" vessel was seized by police in Brindisi, in the southern region of Puglia, after "numerous public complaints".

The ship "was hosting over 2,500 police agents, gathered in Puglia for G7 security", COISP Secretary General Domenico Pianese said.

He cited "terrible sanitary conditions: dirty and damaged accommodation, unusable toilets, dilapidated showers, flooded cabins".

On Monday, another union, the SILF, said the police had been "packed like mice" inside the cruise ship, prompting Italy's department for public security to confirm Tuesday that they were being moved to hotels because of the "hygienic-sanitary conditions".

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 (86 Fahrenheit), while water dripped from ceilings.

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

The accommodations aboard the vessel, formerly a Costa Cruises ship but now owned by the Greek ferry operator Seajets, stood in sharp contrast with those awaiting the leaders from the Group of Seven advanced nations, who will gather at a luxurious beachside resort for the G7 talks.

Police and soldiers across Italy have been deployed to the area for the three-day summit beginning Thursday at the five-star Borgo Egnazia resort between Bari and Brindisi on the Adriatic coast.