Results in crucial elections in Italy show no clear winner and raise the possibility of a hung parliament.
The uncertainty does not help the nation's efforts to pass the tough reforms it needs to heal its economic woes and prevent a new round of global financial turmoil.
In the lower chamber of parliament, the Democratic Party leader Pier Luigi Bersani and his leftist coalition scraped a razor-thin victory over Silvio Berlusconi's centre-right, winning by 29.55% to 29.18% with 99.9% of the ballots counted.
But in the 305-seat Senate, preliminary results from the interior ministry showed that the coalition led by former Prime Minister Mr Berlusconi could win 110 seats to the left's 97 seats, with neither group winning a majority, which is required in both chambers of parliament to form a government.
This leaves Italy in a state of limbo with a hung parliament that is unprecedented in its post-war history.
"It is clear to everyone that this is a very delicate situation for the country," Mr Luigi Bersani said.
US stocks closed sharply lower with the Dow Jones Industrial Average down 1.55% on the news. Stocks in Tokyo opened 1.83% lower.
The new Five Star Movement (M5S) led by former comedian-turned activist Beppe Grillo, who has stirred anger at politicians and budget cuts, became the country's third political force, creating dozens of new lawmakers.
Comparing single parties without coalitions, the M5S is now the biggest party in the lower house with 25.55% to the Democratic Party's 25.41% - a shock success that analysts predicted would reverberate around an austerity-weary Europe.
"This is fantastic! We will be an extraordinary force!" Mr Grillo said on his website, warning mainstream politicians they would "only last a few more months".
"We'll have 110 people in parliament and we'll be millions outside."
European capitals fear the lack of a clear winner could bring fresh instability to the eurozone's third largest economy after Germany and France and plunge it back into the debt crisis storm.
Some Democratic Party officials suggested fresh elections may have to be held within a few months after a reform of Italy's complex electoral laws. Others said some form of agreement could be found with the anti-austerity Five Star Movement.
Political analysts suggested a possible return to the grand coalition agreement between right and left seen over the past 18 months, or even dissolving the Senate alone to hold fresh elections for only one chamber of parliament.
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