A century after the great ship went down with the loss of 1500 lives, events around the globe are marking a tragedy that retains a titanic grip on the world's imagination - an icon of Edwardian luxury that became, in a few dark hours 100 years ago, an enduring emblem of tragedy.

Helen Edwards, one of 1309 passengers on memorial cruise aboard the liner Balmoral who have spent the past week steeped in the Titanic's history and symbolism, said on Saturday the story's continuing appeal was due to its strong mixture of romance and tragedy, history and fate.

'(There are) all the factors that came together for the ship to be right there, then, to hit that iceberg. All the stories of the passengers who ended up on the ship,' said Edwards, a 62-year-old retiree from Silver Spring, Maryland.

'It's just a microcosm of social history, personal histories, nautical histories.'

The world's largest and most luxurious ocean liner, Titanic was traveling from England to New York, carrying everyone from plutocrats to penniless emigrants, when it struck an iceberg at 11.40pm on April 14, 1912. It sank less than three hours later, with the loss of more than 1500 of the 2208 passengers and crew.

Aboard the Balmoral, a cruise ship taking history buffs and descendants of Titanic victims on the route of the doomed voyage, passengers and crew will hold two ceremonies at the site of the disaster, 640km off the coast of Newfoundland - one marking the time when the ship hit the iceberg, the other the moment it sank below the waves.

At 2.20am (1547 AEST) ship's time on Sunday a minister will lead prayers, floral wreaths will be thrown into the sea and a shipboard band will play Nearer My God To Thee, the tune the Titanic's band played as the vessel went down.

Passengers aboard the cruise, which left Southampton on April 8, have enjoyed lectures on Titanic history, as well as the usual cruise-ship recreations. Many have dressed in period costume for elaborate balls and a formal dinner recreating the last meal served aboard the ship.

Some of the passengers have a direct link to the ship, through an ancestor who was on board. Most feel some sort of connection to an event whose ripples have resonated for a century.

Another cruise ship, Journey, left New York on Tuesday and will join Balmoral at the site.

In Belfast, where the Titanic was built - the pride of the Harland Wolff shipyard - thousands attended a choral requiem at the Anglican St Anne's Cathedral or a nationally televised concert at the city's Waterfront Hall on Saturday.

The city spent decades scarred by its link to the disaster, but has come to take pride in the feats of engineering and industry involved in building the Titanic.

In Southampton, an orchestra played composer Gavin Bryars' work The Sinking of the Titanic, and a commemoration is planned in Halifax, Nova Scotia, where more than 100 victims of the tragedy are buried.