Inflation is estimated to have risen to an annual rate of 5% in September, according to the latest "flash" estimate from the Central Statistics Office.

This compares to 4.9% in August and marks the second month in a row that inflation has risen.

Inflation is estimated to have risen marginally by 0.1% from August to September.

Energy costs rose sharply in the month by 3.7%, and are up 9% on an annual basis. This is reflected in higher home heating oil prices and higher prices for diesel and petrol.

Petrol and diesel prices have both risen off the back of higher prices on the wholesale market and the partial reversal of a cut in excise duties on September 1.

But despite the rise in energy costs, transport costs fell sharply last month, based on a seasonal reduction in air fares. Transport costs fell by 1.2% in the month and are up 0.8% compared to September last year.

Today's figures show that food prices rose by 0.4% in the month and are up 7.5% on an annual basis. This compares to an annual rate of food inflation of 8.2% in August.

When energy and unprocessed food prices are stripped out, so-called core inflation is estimated to be 4.5%. This compares to core inflation of 4.8% in August.

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This "flash estimate" is the Harmonised Index of Consumer Prices (HICP) measure of inflation, which is used to compare prices across the EU and euro areas.

The official measure of inflation in Ireland is the Consumer Price Index (CPI), which showed an annual inflation rate of 6.3% last month.

The biggest difference between the two measures is that the CPI includes mortgage interest repayments, which have risen steeply over the past year.

Final figures for both CPI and HICP in Ireland will be published by the CSO on October 12.

Euro area flash estimates for September will be published by Eurostat tomorrow.

Euro area inflation was 5.2% in August.