U.S. annual inflation continued to ease in September as the energy price index weakened.

The unadjusted consumer price index grew 2.3% year over year in September, following a 2.7% increase in August, the U.S. Labor Department said. Econoday had predicted the index would tick up 2.4%.

Energy prices rose 4.8% year over year, slower than the 10.2% annual increase in August.

On a seasonally adjusted monthly basis, consumer prices went up 0.1% in September, following a 0.2% increase in the prior month. Energy prices were down 0.5% month over month.

Core prices, which exclude food and energy, rose 2.2% year over year, unchanged from the rate of increase in August but slightly lower than Econoday's 2.3% forecast.

Core inflation in monthly terms was also unchanged at 0.1% in September.