LONDON: Spanish 10-year government bond yields rose back above 6 percent on Wednesday on fresh concerns about the country after finanical sources said its ailing banks could be forced to raise new money to cover property loans.

Spain will demand banks set aside another 35 billion euros ($45 billion) against loans to builders, the sources said, as it battles to rebuild confidence in a sector where huge losses have raised fears the country may need an international bailout.

Spanish 10-year yields rose 16 basis points to 6.03 percent, rising back above the 6 percent mark that could see the rise in yields accelerate if the break is sustained.

"We've spent a lot of time consolidating in this region and a break of (the top of the recent range) at 6.16 (percent) is the next one to watch," a trader said.

Spanish credit default swaps raises 19 basis points to 512 bps, according to provider Markit.

Equivalent Italian yields and CDS were also higher, with political uncertainty in Greece helping to undermine sentiment in peripheral euro zone debt.