Spain's borrowing costs surged at its first auction since becoming the fourth euro member to seek a bailout, with the Treasury paying the most for at least eight years to sell debt for one year.

The Treasury sold 2.4 billion euros ($3 billion) of 12- month bills at an average rate of 5.074 percent, 2.1 percentage points more than the 2.985 percent paid on May 14. It also sold 639.3 million euros of 18-month debt at 5.107 percent, compared with 3.302 percent last month, the Madrid-based Bank of Spain said today.

The euro area's fourth-largest economy, which is due to sell 2 billion euros of bonds on June 21, is urging European authorities to act so it doesn't lose access to financial markets. Its bonds have dropped to euro-era lows since requesting as much as 100 billion euros of aid to shore up its banks on June 9.