The annual rate of inflation jumped to 5.33% in September, the highest rate this year. In August, the annual inflation was 3.88%, the statistics institute INS said.

Monthly inflation rose to 1.18%, after a 0.5% increase in August.

“The inflation rate in September produced a negative surprise and came in above our expectations of 4.6%,” Austria’s Erste Group Bank AG said in a short report Wednesday.

The bank revised upward its annual inflation forecast to 5.5% in December, from around 4% previously, saying it expects the rate will remain above the central bank’s target throughout 2013 as well.

“Higher excise for tobacco, energy and alcohol beginning with January 2013 and the planned increases in the administered price of energy at the request of the IMF and EU are the main inflationary drivers,” Erste said.

The unexpected surge in September prices also prompted Raiffeisen Bank to modify its year-end forecast to around 5.5%, from 4.5% initially.

“There is a high probability food prices will increase faster than expected in the coming months,” Raiffeisen said.

Food items were 2.3% costlier on the month in September, while prices in the non-food and services sectors rose 0.6% and 0.4%, respectively, INS data showed.

Romanians paid by 27.4% more for potatoes in September compared with August, while eggs were by 7.2% more expensive.

In the non-food sector, fuel prices increased 1.6% on the month, while the price of natural gas went up 2.8%, the data showed. Water and sewage services were 2.2% costlier on the month.

Romania’s harmonized index of consumer prices, or HICP, rose slightly to 3.1% at the end of September, from 2.9% the month before.

The central bank targets an annual inflation of 3% at the end of 2012, plus/minus one percentage point around the band.

Last month, the bank kept its key rate unchanged at 5.25% a year and warned of heightened inflationary risks due to higher global and domestic food prices.