Petrol prices have hit their highest level since the start of the Iran-US war.

Fuel monitoring site Gaspy today showed the average price of 91 unleaded at $3.50.5

Gaspy director Mike Newton says that price is slightly higher than the $3.50.2 hit at the peak of the war back in April.

The latest increase follows a sustained period over where the price of Brent crude has sat above $US100 ($NZ179) a barrel.

It is currently at $US101.5.

The New Zealand dollar has also fallen sharply over the last couple of months, down around 7% since August to be currently at around 55.8 US cents. That's near one-year lows.

A lower kiwi dollar makes imports of fuel more expensive.