The anti-establishment 5-Star Movement looked set to easily win the election for the mayor of Rome on Sunday and clinch a surprise victory in Turin, in a major setback for Prime Minister Matteo Renzi.
The result is a breakthrough for 5-Star and is likely to pile pressure on Renzi, who faces a crucial referendum on constitutional reform in October on which he has staked his political career.
The prime minister has struggled to boost economic growth after years of stagnation and been hurt by scandals in the banking sector. He has also been criticized by PD hardliners, who say he has moved his party too far to the right.
In the run-off ballot in Rome, the 5-Star candidate, Virginia Raggi was on course to win a commanding 67 percent of the vote, against 33 percent for the center-left's Roberto Giachetti, making her the capital's first woman mayor.