Greek government bonds were the hardest hit as a sharp sell-off gripped financial markets for a second day, with 10-year yields rising to nearly 9 percent, while Spain missed its target at a bond auction due to weak demand from investors.

With stocks volatile and oil prices plunging, investors sought refuge in safe-haven German bonds, pushing yields on the euro zone benchmark to record lows. [MKTS/GLOB]

ECB President Mario Draghi helped to end the last euro zone crisis by promising two years ago to do whatever it takes to save the euro. This brought down borrowing costs of "peripheral" euro zone countries such as Greece, which had been bailed out by the European Union and IMF, and Spain, which took EU aid to rescue its banks.

Interest rate strategists said investors could increasingly start to question whether the ECB would resort to its ultimate policy weapon for averting a crisis - buying government bonds.

"It's early days ... but if the market loses faith in what monetary policy can do to fend off falling global growth and the risk of deflation, then it could become a much more serious issue," KBC rate strategist Mathias van der Jeugt said.

In the biggest two-day sell off since July 2012, Greek 10-year yields shot up more than 100 basis points (bps) to 8.98 percent on Thursday. While this is well short of the 40 percent peak they reached in 2012, past rises in European peripheral bond yields have picked up pace above 7 percent.

Greece aims to ditch its unpopular bailout programme with the EU and International Monetary Fund, which demanded severe austerity, and return to relying on markets to raise funds, a plan that has worried investors.

Policymakers tried to reassure the markets, with the ECB saying it would loosen the rules on collateral to give Greek commercial banks access to more funding.

Greek Finance Minister Gikas Hardouvelis said the turmoil did not reflect the fundamental state of his country's economy. "Those monitoring markets know that very often they are nervous, excessive in their reactions," he told parliament.

Compared with Germany, the premium or "spread" that Greece pays to borrow over 10-years was the highest in more than a year. Italy's was at five-month highs, Portugal's at seven-month highs and Spain's at two-month highs.

Italian 10-year yields rose 19 bps to 2.58 percent, Portuguese yields were up 34 basis points at 3.64 percent while Spain's were up 11 bps at 2.20 percent. By contrast Bunds, the German equivalents, hit a new low of just 0.716 percent before rising to 0.78 percent after the release of strong U.S. employment and industrial output data.

In Thursday's auction Spain sold only 3.2 billion euros ($4.09 billion) of debt due to weak demand, falling short of the top end of its target amount.

"(This is) the first time I can remember this happening in quite some time ... This weakness is unsurprising given the very chunky increase seen in all euro zone spreads versus the Bund this morning," said Lyn Graham-Taylor, a strategist at Rabobank.

French five-year bonds sold at a new record low yield at an auction as investors took shelter in liquid, high-rated debt, but in secondary markets its yields were up 6 bps at 1.2 percent.

OPPOSING VIEWS

Market jitters were made worse by a rift in Brussels as France and Italy present 2015 budgets that appear to break EU targets.

German Chancellor Angela Merkel told parliament on Thursday that Europe must cut public deficits and improve competitiveness because the euro zone debt crisis had not yet been overcome and its causes had not been eliminated.

There is also a debate in Europe's top court over whether the ECB's promise to buy euro zone government bonds if this were needed to save the euro would breach of its mandate and amount to direct monetary financing of governments.

If the challenges made by German lawmakers are upheld, it would probably torpedo an ECB programme to buy government bonds that investors are depending on.

"The ECB only has one card left to play and it doesn't look imminent," said one government bonds trader.

(Additional reporting by Michael Urquhart; editing by David Stamp)

By John Geddie

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