Petrol prices in many parts of the country have crossed $2.40 for the first time, days out from a nationwide tax increase.

Stations in Wellington and many parts of the South Island, and others which use the so-called "national price" are now charging $2.409 a litre for regular petrol, the latest in a series of record highs seen in recent weeks.

In Tauranga fuel prices remain below this, sitting at about $2.097 to $2.209 a litre for regular petrol, according to latest figures by Gaspy.

On a nationwide scale, all of the major fuel companies appear to have raised prices overnight.

From the start of October motorists will face another hit, when a nationwide 3.5c a litre excise tax is added. Including GST, the increase is expected to see 4c a litre added to petrol prices across New Zealand.

Diesel prices, at $1.809, are at the highest level in just over a decade.

Overnight Brent crude, the international benchmark for crude oil, climbed above US$81 a barrel, the highest since 2014, amid concerns about global supplies. According to reports, some traders are speculating oil could return to US$100 a barrel in the coming months.

In recent days US president Donald Trump has entered the debate over oil prices, tweeting that oil cartel OPEC "must get prices down now".

Additional reporting Stuff.co.nz