Euro zone consumer prices grew 0.3% year-on-year in January, the European Union's statistics office said today, revising downward its earlier estimate of a 0.4% rise. 

The annual inflation figure for January was below expectations. Economists polled by Reuters had forecast an increase of 0.4%. 

Inflation is, however, slightly accelerating compared to December, when prices in the euro zone rose 0.2%.

Eurostat said that on a monthly basis, prices in the euro zone dropped in January by 1.4%, as expected. 

Excluding the volatile prices of unprocessed food and fuel, or what the European Central Bank calls core inflation, prices increased in January by 1%.

This was in line with forecasts and more than the 0.9% rise recorded in December. 

The new figures add to the ECB's policy headaches.

The European Central Bank wants to keep headline inflation below, but close to, 2% and has been buying billions of euros of euro zone government bonds to inject more cash into the economy and accelerate price growth.

Energy prices were confirmed as the main drag on euro zone inflation. They dropped 5.4% in January on a yearly basis, more than the 5.3% decrease previously estimated by Eurostat. 

The drop in energy prices, driven by plummeting oil prices, is however slowing down from the 5.8% decrease recorded in December, a downward trend started in October. 

Unprocessed food was the main factor driving prices up in the euro zone, marking an annual 1.4% increase, which was however lower than the 1.8% rise earlier estimated by Eurostat. 

In December, unprocessed food prices had increased by 2%.