Former Prime Minister Silvio Berlusconi's right-wing coalition was leading the Italian election. However it is unlikely to reach a majority in Parliament, suggesting weeks of drawn-out negotiations to find a broader coalition amid growing populist anger over migration and the weak economy.
The Five-Star Movement was expected to come in second in a campaign marred by neo-fascist rhetoric and anti-migrant violence.
Economic analysts said the uncertainty would send tremors through financial markets.