Spain's stock market suspended trade in Bankia's plunging shares on Friday as media reports said the struggling lender may seek up to 20 billion euros ($A25 billion) from the state to stay afloat.
Bankia requested the suspension ahead of a board meeting to decide on a recapitalisation plan, "in view of the lack of precision on the figures" ahead of its decision, the bank said in a statement.
Bankia's shares plummeted 7.43 percent on Thursday to close at 1.57 euros, taking total losses to more than 58 percent since their listing in July 2011 when Bankia was formed by the merger of seven savings banks.
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Spain's fourth-biggest bank, Bankia was partially nationalised this month as the state tried to save it from its vast exposure to the troubled property sector.
The state took a controlling 45-percent stake by converting a loan of 4.465 billion euros to its parent group Banco Financiero de Ahorros (BFA) into equity.
Newspaper reports Friday said the bank's total capital needs could be much higher.
Leading daily El Pais, citing market sources, said Bankia could ask for an additional 15 billion euros to cushion it against real estate-related assets, whose value has crumbled since a 2008 property crash.
That would bring the total state bill close to 20 billion euros.
Business daily El Economista quoted sources close to the situation as saying Bankia could ask for public aid of 15-20 billion euros.
Economy Minister Luis de Guindos told parliament Wednesday the government would provide any capital needed to turn the bank around.
He said the "viability plan" to be drawn up by the board Friday must specify the capital required to fully meet tougher new banking rules introduced by government reforms in February and May.
The extra cash must include 7.1 billion euros to be set aside by Bankia to cover its property-related assets and a further 1.9 billion euros to boost capital levels on its books, he said.
Bankia's viability plan would also have to satisfy its auditors, he said, after they refused to sign off on the bank's 2011 accounts because of reservations about its asset valuations.
Prime Minister Mariano Rajoy's conservative government this month instructed Spain's banks to set aside an extra 30 billion euros in 2012 in case property-related loans go bad.
That was on top of 53.8 billion euros in provisions required under reforms enacted in February.
As part of the latest reform, the government has named independent auditors to verify the banks' balance sheets, which were estimated by the Bank of Spain to hold 184 billion euros in problematic loans at the end of 2011, 60 percent of their total property portfolio.
