Heritage campaigners in Montenegro have accused developers of turning an historic island fortress, where prisoners were once starved and tortured, into a “haven for the rich” as its conversion into a five-star resort gets underway.

The island of Lastavica, on which the 19th century Mamula fortress is built, occupies an idyllic position off the coast of the tiny Balkan country, which is undergoing a tourism boom as investors move in on its beaches and bays.

But the island has a dark, haunted past – during the Second World War it was used by the occupying Italians as a place to incarcerate around 2,000 political prisoners.

Many were tortured and an estimated 130 were killed or starved to death in the fort’s bleak cells.

After decades of abandonment, the Montenegrin government agreed in 2016 to grant a 49-year lease on the island to a development company, which has begun building work to turn the fortress into a luxury resort complete with water sports club, restaurants and bars and three swimming pools. The boutique hotel will boast a spa and 34 rooms.