Petrol prices are again on the rise after plummeting to their lowest level in six years in January.

The Australian Competition and Consumer Commission (ACCC) says petrol prices in Sydney, Melbourne, Brisbane, Adelaide, and Perth fell 14.6 cents per litre (cpl) to an average 109.2cpl in January.

That was their lowest average price since January 2009.

But the ACCC says the price at the bowser lifted in February, resulting in a narrower gap between prices in the city and the country, where the cost of petrol has remained higher.

“Retail petrol prices in the five largest cities started to increase in February 2015, so we would expect the differential to narrow in the remainder of the March quarter 2015,” ACCC chairman, Rod Sims, said on Thursday.

Sims said the ACCC would monitor regional prices in the three months ahead.

The rise in February was due to a rebound in international petrol prices, the watchdog said.

Of the five largest cites, Perth recorded the highest monthly average petrol price in January of 115.0cpl.

That was followed by Brisbane (112.4cpl), Melbourne (108.1cpl), Adelaide (105.8cpl) and Sydney (104.6cpl).

Overall, Darwin was the most expensive capital city in which to buy petrol, with drivers paying an average 135.4cpl.

On Thursday morning, the cheapest petrol in Sydney was 112.0cpl at a service station Pennant Hills, according to monitoring website motormouth.com.au.

In Melbourne, petrol was cheapest at 107.5cpl at an outlet at Trafalgar.

AAP