The yield on Spain's 10-year bond yield rose to hit 6.81 per cent in afternoon trading, according to data provider FactSet, while stocks see-sawed and were down slightly just before markets closed.
The bond rate seen as a measure of a nation's financial health fell back to 6.67 per cent in late trading. That's the same level as Spain's previous record — set on May 30 as the country's economic woes multiplied, and last November after the then-ruling Socialist Party was ousted by the conservative Popular Party.
The latest yield brings Spain's borrowing costs dangerously high to seven per cent — close to the level at which Greece, Ireland and Portugal sought an international bailout.
Investors continued to find more questions than answers in the country's decision to seek help for its ailing bank sector by tapping a €100 billion (US$125 billion) eurozone bailout fund.
But investors are worried it will not solve the country's problem as the government may have trouble paying the money back.
Fitch said in a statement that its downgrade of the banks was a result of a previous downgrade of the Spanish sovereign debt on June 7. Fitch said it had conducted stress tests, both on the Spanish banking sector as a whole and on individual banks, updating results from tests done in 2011.
The ratings agency said the weakness of the Spanish economy would continue to have a negative effect on business volumes "which, together with low interest rates, will place pressure on revenues."
There has been growing concern that an increasingly large amount of Spanish government debt is being bought by its banks as the country finds fewer and fewer international buyers for its bonds. As Spain's banks continue to struggle, weighed down by their toxic property loans and assets, the government is finding it increasingly harder to sell its bonds.
The rescue package for Spain's crippled lenders was announced Saturday by finance ministers from the 17-country euro area, but the exact amount the country's banks will receive has not yet been published.
It is not yet clear where the euro area bailout loans will come from. If the money comes from the existing eurozone rescue fund, the European Financial Stability Facility, its repayments will have the same priority as the all the other private bond investors. However, if the funds are to come from the new bailout facility, the European Stability Mechanism, its bond repayments will be given a higher priority than everyone else's — which could mean that other debt would be less likely to be paid off. That could make bondholders less willing to buy Spain's debt or demand a higher interest rate to compensate for the added risk of losses.
Spain will wait for the results of two independent audits of the country's banking industry before saying how much of the €100 billion it will tap.
In a report released late last week, the International Monetary Fund estimated Spain needs around €40 billion to prop up banks hurting from an unprecedented real estate boom that went bust.
Investors also want to know whether Spain will ask for a safety margin of extra money to cushion itself against a further shock, such as a deterioration in the economy.
While Spain's bailout is designed to prop up its banks, investors are also worried that the Spanish government might eventually be forced into asking for a bailout to help it pay its way. Recession-hit Spain, which has the eurozone's fourth-largest economy with unemployment of nearly 25 per cent, may be too big for the eurozone's rescue funds to handle.
Associated Press Writer Daniel Woolls contributed from Madrid.