U.S. consumer prices were flat in April, largely because of a decline in gas prices, the Labor Department reported Tuesday.

The Consumer Price Index (CPI), which tracks inflation at the retail level, was unchanged in April on a seasonally adjusted basis, following a 0.3 percent increase in March.

The report said energy index, which had risen in each of the three previous months, declined 1.7 percent in April and offset increase in the other major categories. Gas prices fell 2.6 percent last month after rising sharply over the first three months of the year.

In April, food costs edged up 0.2 percent.

Excluding the volatile food and energy categories, the so- called "core" index rose 0.2 percent in April, the same increase as in March.

Over the last 12 months, the all items index increased 2.3 percent before seasonal adjustment.

The CPI is a key barometer for monetary policy decision of the U.S. Federal Reserve. The central bank anticipated that the increase in gas prices earlier this year would affect inflation only temporarily and the inflation would subsequently fall to a reasonable level.