Italian Premier Mario Monti's announcement that he plans to resign has sent the interest rate for Spain's benchmark 10-year bond climbing again.
The rate, an indication of investor appetite, rose 0.19 percentage points to 5.84% in opening trading this morning.
It later edged back to 5.59%. The yield had dropped to 5.3% last week.
The main IBEX stock index in Madrid was down 2% this morning.
Spain and Italy are two countries at the centre of the European debt crisis.
Recession-hit Spain's borrowing costs rose to unsustainable highs of 7% earlier this year but have eased greatly since the European Central Bank pledged in September to buy up a country's short-term bonds if it formally applies for aid.
