Italy raised $7.9 billion in bonds on Thursday at unexpectedly high rates, against a background of high tension over the eurozone debt crisis.

The Treasury issued $3.94 billion in five-year bonds and $3.94 billion in 15-year bonds, the Bank of Italy said in a statement.

The yield was 3.67 per cent for five-year bonds compared to 3.24 at the last sale, and 5.06 per cent for the 15-year bonds compared to 4.81 per cent.

The amount raised was the maximum expected in a critical test for Italy's credibility in the financial markets. The sale reflected the new confidence of investors reassured by Portugal's successful bond sale on Wednesday.

The auction was over-subscribed, with the Treasury receiving $11.17 billion in bids.