The mayor of Venice and more than 30 other people have been arrested in a sweeping corruption investigation related to the construction of underwater barriers to protect the historic city from flooding, the latest in a series of Italian bribery investigations involving high-profile public works projects.

Italian financial police confirmed that the mayor, Giorgio Orsoni, had been arrested. The ANSA news agency said he was being investigated for alleged corruption, extortion and money laundering.

The arrests were the result of a three-year investigation that led to the arrest last summer of the head of the consortium building the ambitious but long-delayed system of so-called Moses barriers. Authorities say €20m ($27m) was diverted abroad to bribe politicians.

The first of the underwater barriers was installed last year.

A series of unrelated corruption investigations, mostly involving bribery or embezzlement accusations, have implicated former high-ranking government ministers in recent months. Investigations have revolved around some of the biggest Italian public works projects including the Milan world's fair, Expo 2015, and an Italian-funded water project in Iraq. Most recently, a former interior minister was accused of helping a businessman flee Italy to escape a mafia association sentence.

The string of arrests has prompted comparisons to the "Clean Hands" anti-corruption investigations of the 1990s that toppled an entire political class. The one clear difference this time is that the alleged bribery involves individuals from across the political spectrum rather than political parties enriching themselves.

Wednesday's arrests put more pressure on the prime minister, Matteo Renzi, to take action, after his appointment of an anti-corruption tsar earlier this year. Over the weekend, the European commission flagged the deep-rooted problem of corruption as an issue hampering investment and economic renewal in Italy, which ranked 69th in Transparency International's perceived level of public sector corruption last year – behind Montenegro and just ahead of Kuwait.