All eyes are on Milan, Berlusconi's centre-right stronghold and hometown, where the incumbent, Letizia Moratti, is expected to retain her post. But she may not have enough votes to avoid a runoff later this month.

The 74-year-old prime minister has campaigned vigorously on Moratti's behalf in the northern financial city, even heading the electoral list there.

While his term is not due to expire until 2013, the premier barely scraped through a confidence vote in December and has been plagued by accusations of having sex with an underage prostitute and using his authority to cover it up. About a quarter of Italy's 49 million-strong voters are eligible to cast ballots, with weak growth, unemployment and local issues such as the chronic waste disposal crisis in Naples, uppermost in their minds.

The embattled Berlusconi, who is due in court in Milan later in the morning as a defendant in a bribery trial, is unlikely to comment on the elections which are blanketed by an "election silence" until 1300 GMT.

Currently a defendant in three trials in Milan, Berlusconi's popularity reached a record low of 31 percent in a recent survey.

The elections involve 1,310 communal administrations -- around 16 percent of the total -- including Bologna, Naples and Turin in addition to Milan. Centre-left incumbents are expected to hold on to the traditionally "red" cities of Bologna and Turin.

Naples is less certain as the southern city faces yet another waste disposal crisis.

Despite promises by local authorities and the central government to fix the city's garbage problems, Naples has recently been swamped with waste, prompting Berlusconi to dispatch military troops to the region to help clean up.

The outcome in Naples will likely hinge on the second-round run-off.
A second round is set for May 29 and 30.