Italy's government has declared a state of emergency in flood-ravaged Venice, to help swiftly secure the historic city funds to repair damage from the highest tide in 50 years.

A cabinet meeting on Thursday afternoon approved a special decree including the first measures aimed at helping the city's recovery.

Prime Minister Giuseppe Conte described the flooding as ``a blow to the heart of our country.``

"The cabinet has approved the state of emergency in Venice," Conte tweeted after Tuesday's devastating flooding, also announcing the release of 20 million euros "for the most urgent interventions".

Venice's mayor has said the damage is estimated at ``hundreds of millions of euros.``

Conte spent Wednesday night in Venice, where world-famous monuments, homes and businesses were hit hard by the exceptional flooding.

The water reached 1.87 meters above sea level Tuesday, the second-highest level ever recorded in the city.