Catalan parties pushing for a referendum on breaking away from Spain won strong backing in an election Sunday, while voters punished the rich region's leader Artur Mas, forcing him to share power.

The result could set Catalonia up for a clash with Spain's central government, already riled by Mas's push for greater self-determination as Spain fights to avoid getting bailed out by its EU neighbours.

But it was unclear how Mas would move forward after he saw his support plunge in favour of rival parties that share his desire for some kind of referendum but not all his political objectives.

Mas's centre-right Convergence and Union alliance (CiU) won the vote, but its share of the parliamentary seats plunged to 50 from 62, while left-wing nationalists ERC surged to 21 seats from 10, official results showed.

"We are clearly the only force that can lead this government, but we cannot lead it alone. We need shared responsibility," Mas told supporters in Barcelona afterwards.

"The presidency must be taken up, but we will also have to reflect along with other forces," said Mas, who had vowed to hold a referendum on "self-determination" if Sunday's vote gave him a strong mandate.

Though a humiliating setback to Mas, who called the election two years early after Madrid rejected his demands for greater fiscal powers, the vote gave forces favoring Catalan statehood a commanding majority overall in the 135-seat parliament.

"Support for sovereignty still comes out stronger because the ERC wins extraordinary force," said one of Mas's supporters, Jordi Fiol, 58, waiting for the CiU leader to appear Sunday evening at Barcelona's luxury Majestic hotel.

"What the people really wanted was a pro-sovereignty majority, more than a victory by one party or another," said another, Laia Bartomeus, a 32-year-old lawyer.

The Socialists, the main opposition party nationally, came third in Catalonia as their share fell to 20 seats from 28 and Spanish Prime Minister Mariano Rajoy's Popular Party scored 19.

The prospect of a break-up of Spain had overwhelmed debate about the region's sky-high public debt, savage spending cuts, unemployment and recession.

From windows and balconies hung the red-and-yellow striped flag of Catalonia and the pro-independence flag that also incorporates a blue square with a white star.

An independent Catalonia seemed far off, however.

Rajoy says a referendum on self-determination would flout the constitution and hurt all Spaniards who are already suffering in a recession with the unemployment rate higher than 25 percent.

Catalonia, which traces its origins back more than a millennium, is proud of its language and culture, both of which were suppressed under the rule of General Francisco Franco, who died in 1975.

Mas, like many Catalans, accuses Madrid of raising far more in taxes from the region than it returns, and estimates the gap, or fiscal deficit, at 16 billion euros ($21 billion) a year -- a figure Madrid disputes.

"After he wins, I would like President Mas to face up to Madrid, so they give us back the money they owe us, and call a referendum," said one voter, Gerard Ruiz, 38, a metal worker.

"Now we have started out on this road, we have to go all the way. We want to be an independent people."

Catalans would vote in favor of a referendum on self-determination by 46 percent against 42 percent, according to a survey last weekend in leading daily El Pais.

The region of 7.5 million people accounts for more than one-fifth of Spain's economic output and a quarter of its exports, and boasts one of the world's best football teams, Barcelona FC.

But Catalonia also has a 44-billion-euro debt, equal to one-fifth of its output, and was forced to turn to Madrid this year for more than five billion euros to help make the payments.

For Pedro Nueno, an economist at IESE business school, the result "shows that people are angry because none of the politicians has put forward a clear plan to deal with our country's serious problems: debt, unemployment, finance." (AFP)