Furious Spaniards who say banks cheated them of their savings took to the streets Saturday demanding that the bailed-out lenders give them their money back.

"Thieves! Where is our money?" bellowed a crowd of some 1,000 protesters, many of them elderly, outside the central bank in Madrid before marching on the offices of Bankia, the ruined finance giant.

The protesters say Bankia told them it was putting their money in secure savings products but actually sold them "preferential shares" as it scrambled to raise funds after the financial crisis started in 2008.

Now that Bankia and other lenders have collapsed and had to be rescued with funds from Spain's European partners, customers stand to lose a big chunk of their savings.

The banking consumers' group ADICAE, which has brought legal action against Bankia, planned similar demonstrations in more than 20 towns on Saturday.

Its president Manuel Pardos said in a statement the customers were "victims of a massive fraud" and were now being subjected to "illegal imposed losses".

The European Union on Wednesday gave a green light for the payment of the first slice of the rescue aid, some 37 billion euros ($48 billion), for Bankia and three other Spanish banks.

To meet the conditions demanded by Brussels, Bankia said holders of the so-called "preferentials" would be repaid in shares worth only 61 percent of the value of the money they put in the bank.

"They want to take away 40 percent from us," said one protester, Paloma, 59, who put 25,000 euros into preferential shares, being told she would get the money back after five years.

"I spent 25 years saving a little each day and now when I need it they won't give it to me," said Paloma, who asked not to be identified by her surname.

Spanish banks were brought low by the collapse of a construction boom in 2008 that threw millions into unemployment and poverty. Spain is deep in recession, with one in four workers unemployed.

"They should give back all the money because now in the crisis we don't have any," Paloma said.