Italian police said on Wednesday they had seized assets worth more than 1.6 billion euros from five Sicilian siblings suspected of links to the island's Cosa Nostra mafia.

The criminal group allegedly helped the three brothers and two sisters, described as "businesspeople" from the area around the Sicilian capital, Palermo, to receive construction contracts related to public works.

Palermo police said in a statement they had sequestered real said was one of the biggest of its kind they had ever carried out.

Cosa Nostra, along with the Calabrian 'Ndrangheta and the Camorra around Naples, has long plagued Italy, and in recent years their activity has spread to northern cities from their southern heartland. Three years of recession have helped deep-rooted corruption to flourish.

Italy ranking 69th of 177 countries in global anti-corruption group Transparency International's 2014 Corruption Perceptions Index, joint last in the European Union.

Police are due to give further details of the investigation at a press conference in Palermo later on Wednesday.