Italians were voting Monday in the second and last day of a referendum of which the most important of four issues was whether to permanently abandon nuclear power production.
Some 41 per cent of the around 47 million eligible voters had cast their ballots on Sunday, a surprisingly high turnout in Italy where all six referendums held since 1995 have failed to reach the required quorum of a 50-per-cent-plus-one vote, DPA reported.
Prime Minister Silvio Berlusconi and several members of his centre-government said last week that they would stay away and indicated their supporters should do the same.
Polls were scheduled to close at 1300 GMT with results expected later Monday.
The vote is widely seen as a as a plebiscite on Berlusconi after his coalition suffered a surprise defeat in key local elections held last month.
The government has argued that the nuclear issue has been made redundant by a moratorium on nuclear power it introduced in April, a decision made in the wake of the damage caused by a March earthquake and tsunami to nuclear reactors in Japan.
But environmental activists and the centre-left called for a "yes" vote to uphold a ban on nuclear power introduced in a 1987 referendum held one year after the Chernobyl nuclear disaster in Ukraine.
In addition to nuclear power, Italians are also voting on issues related to the privatization of water supplies and the validity of a law exempting top officials - including the premier - from attending trial when busy with government duties. The latter is especially important for Berlusconi who is currently involved in four trials.