(ANSA) - Milan, September 28 - The city council of Seregno near Milan quit Thursday amid a probe into Calabrian 'Ndrangheta mafia infiltration in which centre-right Forza Italia (FI) Mayor Edoardo Mazza was arrested earlier this week. The move came after the resignations of the ruling rightwing populist Northern League and ex-premier Silvio Berlusconi's FI councillors as well as those from the centre-left minority. Tuesday's sweep landed a big blow on the 'Ndrangheta operations in the wealthy northern region of Lombardy Tuesday, with Mazza among 24 arrested and the former deputy governor of the region among those probed.

The police op was linked to a probe into alleged infiltration of Lombardy's political and business world by 'Ndrangheta, Italy's richest, most powerful and dangerous mafia.

Some 21 suspects were taken to jail and three were put under house arrest, including Mazza.

Mazza, who had gained headlines for campaigning against petty crime and beggars, is accused of facilitating the business of an entrepreneur linked to the mafia who, in turn, allegedly got him votes for his election as mayor.

Police said they had a wiretap in which Mazza promises the construction entrepreneur, Antonio Lugara', that he would intervene to get him the contract to build a shopping centre at Seregno.

"Every promise is a debt, isn't it," Mazza allegedly told Lugara'.

Lugara' was among those also arrested in the investigation, sources said.

Former Lombardy deputy governor Mario Mantovani is under investigation for corruption in relation to the probe, sources said.

Mantovani, now a Forza Italia regional councillor, is not probed for mafia crimes.

