E.C.B. Stimulus Calls for 60 Billion Euros in Monthly Bond-Buying

FRANKFURT — The European Central Bank said on Thursday that it would begin buying hundreds of billions of euros worth of government bonds in an aggressive — though some say belated — attempt to prevent the eurozone from becoming trapped in long-term economic stagnation.

The bank’s president, Mario Draghi, said the central bank would begin buying bonds worth 60 billion euros, or about $69.7 billion, a month. That is more spending than the €50 billion a month that many analysts had been expecting.

The long-awaited program, known as quantitative easing, is meant to spur growth in the listless eurozone economy and to raise inflation to healthier levels. In December, inflation in the 19 countries of the eurozone fell below zero and raised the specter of deflation, a sustained decline in prices that can lead to higher unemployment and that is notoriously difficult to reverse.

As a further stimulus step, the European Central Bank also said on Thursday that it was cutting the interest rate it charges on loans to commercial banks, as long as the banks commit to lending that money to companies or individuals. The new rate would be 0.05 percent, down from 0.15 percent.

“We believe the measures taken today will be effective,” Mr. Draghi said at a news conference.

Financial markets greeted the news favorably. The benchmark Euro Stoxx 50-stock index was up 1.6 percent, with financial firms’ shares among the gainers, on hopes that the bond buying will spur growth and lending. Bond yields in some eurozone countries hit new lows, including countries that might benefit most from the central bank’s program. The yields on 10-year government bonds in Italy dropped to 1.56 percent and in Spain to 1.39 percent.

The euro, which had already been near its lowest level in 11 years on expectations of action by the central bank, weakened further against the dollar, falling about 1 percent to around $1.14, a move that could help European exporters.

Top officials of the central bank had signaled clearly that a quantitative easing program was in the offing. But there remained, before the central bank meeting on Thursday, many questions about how large the program would be and whether it would be powerful enough to reverse a two-year decline in inflation.