The ministry said a research programme in May involved "the retrieval of objects from the wreck site (of the HMHS Britannic) for the first time, from depths exceeding 120 metres (394 feet)."

The HMHS Britannic was one of three transatlantic passenger lines built at the Harland and Wolff shipyard in Belfast, the first of which was the infamous RMS Titanic.

Requisitioned by the British Admiralty to be converted into a floating hospital during World War I, it struck a German mine in November 1916 while sailing off the Greek island of Kea.

The vessel sank in less than an hour. Of the 1,065 people on board, 30 died when the ship's propellers snagged two lifeboats, the culture ministry said.

The project to document the wreck and its contents was carried out by an 11-member team composed of professional deep-sea divers, using closed-circuit diving equipment.

The research was organised by British amateur historian Simon Mills, founder of the Britannic Foundation, and supervised by Greece's Ephorate of Underwater Antiquities.

"Conditions at the wreck site were particularly challenging due to currents, depth, and low visibility," it said, adding that certain objects initially selected could not be retrieved due to their location and preservation status.

The retrieved objects include the ship's observation post bell, the portside signal lamp, various items of portable equipment from first and second class, ceramic tiles that had decorated a Turkish bath and a pair of binoculars.

They were transported to the ephorate's laboratories in Athens for further conservation and are set to feature in a permanent exhibition at a new museum of underwater antiquities currently under construction in Piraeus, the ministry said.

The third vessel of the group, the RMS Olympic, sailed from 1911 to 1935, undergoing safety improvements after the Titanic sank in 1912.