GENOA • Engineers have started the delicate task of taking apart Genoa's Morandi motorway bridge, almost six months after its partial collapse during a storm killed 43 people and injured dozens.

Thousands of tonnes of steel, concrete and asphalt have already been removed from the spectacularly truncated high-rise bridge in the northern Italian port city to make it lighter before the "deconstruction" operation began.

"It's an important day, the first step on a path that we hope will be as short as possible," Prime Minister Giuseppe Conte told journalists at the site on Friday.

"The new bridge will be up by the end of the year."

Four powerful strand-jacks positioned on the bridge by an enormous crane began unhooking and slowly lowering a 36m-by-18m concrete slab weighing nearly 1,000 tonnes. The jacks are the same as those used to right the Costa Concordia cruise liner off Tuscany in 2013 after it ran aground and capsized, leaving 32 dead.

Yesterday, the vast slab was slowly lowered to the ground, some 48m below, after a diamond chain saw cut through the entire bridge in two places.

The giant slab will be used as a counterweight for removing other pieces before the bridge's towers are demolished with dynamite.

The operation will help the city move on from the disaster on Aug 14 last year when part of the bridge collapsed, sending dozens of vehicles and tonnes of concrete tumbling to the ground.

Italy's most famous living architect Renzo Piano, a Genoa native who helped design the Pompidou Centre in Paris, has provided the design for the replacement bridge that "will last for 1,000 years".

While the new structure has been designed to look different from the old one, opened in 1967, it will feature 43 lamp poles in memory of those killed.

It is expected to be open to traffic by April 2020, with the demolition of the old structure due to take 190 days.

AGENCE FRANCE-PRESSE