The government sold a total of 5.42 billion euros' ($6.73 billion) worth of bonds.
The rate on five-year bonds rose to 5,84 percent compared to 5.66 percent on May 30, while the yield on those set to expire in 10 years went up to 6.19 percent compared to 6.03 percent, the Bank of Italy said.
Italy, which has come back into the debt crisis line of fire, had to pay much higher rates of return on bond sessions on Tuesday and Wednesday.
The country, which has a massive debt pile of over 120 percent of its Gross Domestic Product, has been hit by a wave of market panic sparked by banking turmoil in Spain and fears the EU summit will produce scarce results.
Prime Minister Mario Monti will hope to persuade sceptics, including Germany, that pooling debt would reduce market tension and bring down the spiralling borrowing costs which have hounded Italy and Spain.