Spain's borrowing costs rose and the gap between Spanish and German bonds hit a record level for the euro era.
The Spanish government announced new bonds to finance debt-struck regions as Spanish banks scrambled to clean up bad loans.
The debt premium -- the extra return investors demand to hold Spanish bonds over their safer German counterparts -- leapt to a euro-era record of 5.16%.
Spain's government said it would approve the issuing of joint bonds -- "hispanobonos" -- by the 17 regional governments next Friday, so as to make it cheaper for them to finance their debts.
"The goal is to reduce the pressure on the regions, which is often greater than the pressure on the state in general, with some regions not able to borrow on the market," a spokeswoman for the Economy Ministry said.
Spain's 17 regional governments have suffered a plunge in tax revenues and soaring debt since the collapse of a decade-long property boom in 2008, and they are struggling to pay suppliers.
Moody's Investors Service last week warned of the deficit challenges as it downgraded its credit rating for economic powerhouse Catalonia and three other regions, Murcia, Andalucia and Extremadura.
Catalonia president Artur Mas called Friday for the central government to approve the use of "hispanobonos", which would be issued for all regions and guaranteed by the state.
His region alone faces debt payments, including refinancing costs, of €13.48 billion in 2012.
Investors also showed deep concern over stricken banks' struggles to strengthen their balance sheets.
The government this month instructed banks to set aside an extra €30 billion in 2012 in case property-related loans go bad, on top of €53.8 billion demanded under reforms enacted in February.
Three Spanish savings banks -- Ibercaja, Liberbank and Caja3 -- announced they would vote on a merger later in the day.
Another lender, Banco Popular, whose long-term debt was downgraded by Standard & Poor's on Friday to junk-bond status, said it was trying to sell its online banking to find the cash to clean up its books.
"Banco Popular is in negotiations for the sale and outsourcing of a majority stake of its internet banking and means of payment businesses, although no agreement has been reached as of today," it said in a statement.
Investors expressed worries after Prime Minister Mariano Rajoy's conservative government said it was considering issuing sovereign debt and injecting it directly into recently nationalised lender Bankia.
In the face of the concerned reaction on markets, an Economy Ministry spokeswoman stressed that the preferred option would be to sell bonds on the market and use the proceeds for the banks.
Bankia's board on Friday asked the state to inject €19 billion to help it abide by more stringent capital rules, in addition to €4.465 billion invested by the state earlier this month.
Spanish media said other troubled banks could need yet another €30 billion.
Providing a grim backdrop, the Bank of Spain issued a report predicting Spain's recession, which began in the last quarter of 2011, would continue at least until mid-2012.
Official data also showed retail sales plummeted 9.8% in April, the steepest monthly drop in since the statistical series began in 2003.
Despite the downturn, Spain's government says it is determined to press ahead with an austerity programme to slash the deficit to 3.0% of economic output by 2013 from 8.9% last year.
But "recent fiscal data suggest that Greece and Spain will struggle to meet their existing budget deficit forecasts for 2012 without implementing further austerity measures," a report by Capital Economics warned.