ROME — Italy's last bond auction of the year saw the country having to pay higher borrowing rates to get investors to lend it the money it needs to rollover its big debts.

Wednesday's auction showed that the debt-riddled country paid an average yield of 6.47 percent for investors to lend it €3 billion ($3.95 billion) over five years.

The yield was up 0.17 percentage point from last time Italy looked to raise money over five years and was the highest rate since 1997. The euro came into existence in 1999.

Italy has seen its borrowing costs, both in the markets and in bond auctions, rise markedly over the past few months as investors have grown increasingly worried over the country's ability to deal with its debts, which total around €1.9 trillion ($2.5 trillion), or around 120 percent of its GDP. It is considered too big to bail out by its partners in the 17-country eurozone.

"Sentiment this morning was fairly bleak to start with, so it's not surprising that Italy's borrowing costs are escalating," said Nicholas Spiro of Spiro Sovereign Strategy. "Italy's predicament is dire: it has become a proxy for eurozone risk at a time when its funding requirements are about to balloon."

As the auction took place, Premier Mario Monti, a technocrat whose appointment was intended to reassure markets that Italy was serious in reforming its finances, faced a protest in the Italian parliament by senators opposed to his government's austerity plans, forcing a brief suspension of the session.

Members of the Northern League, an ally in the previous government led by Silvio Berlusconi, whistled and held up signs saying "Enough Taxes" and calling the austerity program "robbery."

Monti told the Senate Wednesday that his government might consider enacting the so-called Tobin tax on financial transactions as a means of reducing the tax burden on families. Such a tax had been rejected by the Berlusconi government

There have been growing signs of discontent as Monti has rolled out the painful measures, which are expected to be approved by parliament in the next few days before the Christmas break.

On Monday, unions protested against the spending cuts and tax increases the government is seeking to restore investor confidence. Monti has indicated he would make a few small concessions to help families but made clear his intention to push through the entire package.

Investors clearly remain worried about the future of both Italy and the wider 17-nation eurozone despite an EU deal last week to tighten controls on spending. While that deal will boost longer-term budget discipline, it does little to lower current debt and exposed deepening political division.