South Korean officials announced Tuesday that a Chinese-led consortium had won the bidding to take on the massive task of raising the Sewol ferry that sank with the loss of over 300 lives a year ago.

The 6,825-tonne passenger ship sank off the country's southwest coast in April 2014. Most of the dead were children on a school trip.

Nine remain unaccounted for in the accident, which deeply traumatised the nation, and the families of those still missing had led a campaign for the ferry to be brought to the surface.

On Tuesday, the maritime ministry formally named the consortium of China's state-run Shanghai Salvage and a South Korean firm as the final winner of the 85.1 billion-won ($73 million) salvage tender.

Officials noted Shanghai Salvage's experience, including the raising of a cruise ship that sank in China's Yangtze River with the loss of more than 400 lives in June.

The Sewol lies 40 metres (130 feet) down on the sea bed and bringing it to the surface poses a substantial technical challenge.

Preliminary research at the area -- notorious for poor underwater visibility and strong currents -- will begin this month with a goal to finish the salvage operation by July 2016.

"Our top priority is salvaging the ship unscathed and avoiding losing the bodies that are still unaccounted for," the ministry said in a statement.

The project will involve two giant cranes of over 10,000 tonnes and 200 workers including about 100 divers, Shanghai Salvage said.

The accident -- one of the deadliest maritime accidents to hit Asia's fourth-largest economy -- plunged the entire country into months of mourning.

The overloaded Sewol was carrying 476 people, including 325 students from a high school in Ansan, south of Seoul. Only 75 students survived.

The accident -- blamed on the ship's illegal redesign and overloading left unchecked by officials -- prompted public calls to overhaul lax safety standards and tackle deep-rooted corruption.