Flowers have been laid at a makeshift memorial near the ship

Foghorns sounded three times and churchbells tolled, as thousands gathered to mark a minute's silence.

The 15 died, and 30 were injured, when a gangway leading to the world's biggest passenger liner collapsed.

French prosecutors have launched an involuntary manslaughter inquiry into the accident on Cunard's cruise ship.

The Queen Mary 2 is still in dry dock at the port for finishing touches before its maiden voyage in January.

Click here for facts about the ship

In London, Queen Elizabeth II, who is expected to name the ship on 8 January, sent a message of sympathy to the victims' families.

"I was shocked to learn of the loss of life among those visiting the Queen Mary 2 in Sainte Nazaire," she said.

"I extend my deepest sympathy and condolences to the families and friends of those killed and injured in this tragedy. My thoughts and prayers are with them all."

Two groups of families were being shown around the liner when the accident happened on Saturday, according to a spokesman for shipyard owners Alstom.

The victims landed on the concrete floor of the dry dock after a fall of almost 15 metres.

Two friends who died, Charlene Rio and Celine Duchesne, both 20, had just secured temporary jobs on the ship.

Investigation

Their friend Eve Denie, 22, was at the port to pay her respects on Monday.

"This was their first and their last day of work," she said. "And they didn't ever even set foot on the boat."

Many people in the town know someone involved in the incident or someone who has lost someone involved.

Here, everyone feels more or less affected. We're all sad Sylvie Nerand

Sylvie Nerand, 48, who has a friend whose sister died, said: "Here, everyone feels more or less affected. We're all sad."

French President Jacques Chirac visited the site on Sunday to offer condolences to families of the victims.

On Monday, prosecutors opened a judicial investigation into "involuntary homicide and injuries" - a standard legal move to determine whether the company that made and installed the gangway has criminal liability.

The 10m (30ft) walkway from the quayside to the ship had been constructed just the day before it broke. It was put in place by specialist French firm Endel.

A spokesman for shipbuilder Alstom said: "The poor people fell down direct from a height of 15 metres [50 feet] to the bottom of the dock."

Flagship

The ship, destined to be the flagship of British cruise giant Cunard, has been under construction at the Chantiers de l'Atlantique shipyard in Saint Nazaire since 2002.

It completed sea trials a few days ago and is due to sail to her home port of Southampton around Christmas.

The Queen Mary 2 is the largest and most expensive passenger ship ever built, 345 metres long and as tall as a 23-storey building.