The euro zone's annual rate of inflation was lower in February than first estimated, and fell back to the level reached in October 2013 that prompted the European Central Bank's last effort to stimulate growth.

The European Union's statistics agency Monday said consumer prices in the 18 nations that share the euro were 0.3% higher than in January, and 0.7% higher than in February 2013. Eurostat last month estimated that the annual rate of inflation was unchanged at 0.8% in February.

The revision means that inflation dropped further below the ECB's target of just under 2.0%, and to its lowest level since October of last year. Responding to that figure in early November, the ECB cut its benchmark interest rate to a record low of 0.25% from 0.5%, its last policy move.

ECB policy makers have repeatedly said they don't expect outright declines in consumer prices, known as deflation. They reject comparisons with Japan, which struggled with deflation for two decades, saying the ECB has acted more decisively than Japan did in the 1990s and that European banks are stronger.

But they have acknowledged that very low rates of inflation are a worry, and in recent weeks have focused on the role of an appreciating euro in pressing down on import prices and activity.

ECB President Mario Draghi Thursday issued his strongest statement yet that the strong euro is pulling down inflation in the euro zone, making clear that the central bank is concerned that the appreciating euro could undermine the currency bloc's fragile recovery.

"The strengthening of the effective euro exchange over the past one-and-a-half years has certainly had a significant impact on our low rate of inflation and, given current levels of inflation, is therefore becoming increasingly relevant in our assessment of price stability," Mr. Draghi said.

The threat of widespread deflation in the currency area appears to be growing, with four members recording annual declines in consumer prices during February: Greece, Cyprus, Portugal and Slovakia. A number of other members are close to that point, with Ireland and Spain recording annual inflation rates of just 0.1%, while in Slovenia the inflation rate was 0.2%, and in both the Netherlands and Italy it was 0.4%.

However, Mr. Draghi and his colleagues on the ECB's governing council have noted that some of the slowdown in the inflation rate is down to weaker global prices for energy, something over which they have little control. The rise in the core rate of inflation--which excludes volatile items such as energy and food--to 1.0% from 0.8% may reassure them that weak domestic demand is not the main cause of feeble prices rises.

Write to Paul Hannon at paul.hannon@wsj.com