Updated 10.20am

The two remaining towers of the motorway bridge in the Italian city Genoa that collapsed nearly a year go killing 43 people were demolished on Friday to make way for a new structure, authorities said.

The remains of the Morandi bridge were detonated at 9:00 am (0700 GMT), with nearly 4,000 local residents evacuated, the city authorities said.

Explosives were attached to the legs of the towers and the parts of the bridge still standing and the detonation of the 4,500-tonne concrete and metal structure lasted just a few seven seconds.

Water tanks were placed around the towers to prevent the spread of dust.

Italy's Deputy Prime Ministers Matteo Salvini and Luigi Di Maio attended the event. 

The dismantling of the remains of the bridge, which collapsed in bad weather on August 14, 2018, started in February. 

The disaster threw the spotlight on Italy's creaking infrastructure. 

Local residents expressed relief that the eyesore would finally be gone, but were concerned about the possible consequences of the detonation.

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The bridge "is high, it is big, it is full of iron, it is super heavy... I don't know what will happen when it falls. Apart from the dust it will cause, I am worried about the impact," local resident Francesco Russo told AFP TV.

Following the demolition, officials are expected to welcome a ship that will arrive in the city's port transporting the first parts of a new bridge, the construction of which is scheduled to begin next year. 

The government has promised that the new steel and concrete motorway bridge, designed by Italian architect Renzo Piano, will be open for traffic in April 2020. 

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