Investors unimpressed by Spain's banking rescue deal and worried over a possible Greek exit from the eurozone pushed Spain's borrowing costs to near record high on Tuesday.

The nation's risk premium - the extra rate investors demand to hold its 10-year bonds over their safer German counterparts - reached 5.33 percent on Tuesday morning, not far from the euro-era record of 5.48 percentage points struck shortly before Madrid requested a banking rescue on Saturday.

Meanwhile, the yield on Spain's 10-year-bond stood at 6.6 percent. Greece, Ireland and Portugal were forced to seek bailouts from their European Union counterparts when their borrowing costs rose to similar levels.

Analysts believe the instability was caused by the lack of detail over how a lifeline of up to 100 billion euros (about 125 billion U.S. dollars) from the Eurogroup would be deployed to save troubled Spanish banks.

Local media reported that the interest rate for the banking aid loan would be set at three percent. This has still to be confirmed. But Spain's Minister for the Economy and Competitiveness Luis de Guindos said on Saturday that the loan would come with more favorable conditions than the ones provided by the market.