UPDATE 4-Italy centre-left sweeps local elections
* First big vote since inconclusive February national poll
* Centre-left hopes win in Rome can boost its fortunes
* Turnout down sharply, reflecting voter disillusionment
ROME, June 10 (Reuters) - Italy's battered centre-left won the election for mayor of Rome and 15 other major cities on Monday, giving a lift to Prime Minister Enrico Letta and strengthening his leadership of the uneasy coalition with Silvio Berlusconi's centre-right.
The polls, marred by a low turnout, dealt a blow to both Berlusconi's People of Freedom (PDL) party and the anti-establishment 5-Star Movement of comic Beppe Grillo, which stunned Italy by gaining a quarter of the vote in national elections in February.
The centre-left candidate in Rome, former surgeon Ignazio Marino, took 64 percent of votes in a run-off ballot on Sunday and Monday, defeating the incumbent Gianni Alemanno.
"Today is a day that the centre-left has won extraordinary results in many cities across Italy," Marino told reporters. "This is the capital and we need to regain the role of moral leader for our country," he said.
With around 6 million voters in more than 500 towns and cities, the votes were the Letta government's first big test since its formation in April following a long stalemate caused by an inconclusive national election in February.
The grand coalition between Letta's centre-left Democratic Party (PD) and the PDL has aroused little enthusiasm, even among its members, but it was the only viable possibility after no party secured a majority in parliament.
Monday's result underlined broad popular disillusionment with Italy's parties, with a dramatic slump in voter turnout in the capital to 45 percent, down from 63 percent in the run-off in 2008 when Alemanno became mayor.
But the polls were still seen as a significant success for the badly divided PD, which nearly imploded after throwing away the 10-point lead it held ahead of the national election.
"On the whole, the result strengthens the grand coalition government," Letta said. "I'm convinced that today we are capable of doing good work to obtain the results that citizens expect."
The left, which traditionally does well in local elections, won all 16 provincial capitals, including Rome, to regain some momentum after its disastrous start to the year, which saw Pier Luigi Bersani toppled as party leader.
PDL, 5-STAR MOVEMENT LOSES OUT
Grillo's party, which rode a wave of popular discontent to take almost a quarter of the national vote in February, saw almost all its candidates eliminated in the first round two weeks ago. It won only two towns.
It faces an even more telling test in Sicily, where a separate set of local balloting was held on Sunday and Monday. Local elections in Sicily last year gave it one of its greatest triumphs and a formed springboard for its national success.
Preliminary results suggested it had done much less well this time, although it had a chance of reaching the runoff round in the eastern city of Ragusa.
The movement has been shaken by growing concern about Grillo's authoritarian style and his attempts to impose iron party discipline on parliamentarians. Last week two lawmakers left the group, complaining about control over decision-making.
The local elections have no direct impact on national government but the result should reinforce the position of Letta, who has had to struggle with widespread perceptions that Berlusconi is pulling the strings in the coalition.
Although Berlusconi is not a member of the government, the 76-year-old media billionaire has pressed the prime minister for aggressive tax cuts, despite the strained state of Italy's public finances, saying they are a condition for his support.
Berlusconi took little part in the campaign and officials from his centre-right People of Freedom (PDL) acknowledged the party suffered badly as a result.
"At national level, the party is still being pulled up by Berlusconi and that's shown in the opinion polls. That effect doesn't work at local level because we've been slow to build a truly democratic party," said Fabrizio Cicchito, a senior PDL lawmaker.
Letta has pledged measures to lift the economy out of its two-year recession and cut dramatic levels of youth unemployment as well as reforming a sclerotic political system that has repeatedly allowed special interest groups to block reform.
But he faces an uphill struggle with the economy set to contract by 1.3 percent this year according to government forecasts.
Official data on Monday showed the economy shrank by 0.6 percent in the first quarter of this year and industrial output was weaker than expected in April, falling for a third month running and offering no hope that the slump will end soon.