WELLINGTON, March 23 (Xinhua) -- Fuel prices are at their highest level in nearly three years in New Zealand on Wednesday after the four main oil companies increased their prices by 3 cents.

Shell, Caltex, BP and Mobil have raised the price of 91 octane, the most commonly used petrol, to 2.189 NZ dollars (1.6 U.S. dollars) a liter.

And while oil companies exempted Christchurch from the March 8 price increase, motorists there have not been spared the latest rise. Prices in Christchurch have gone up by 5 cents a liter, putting 91 octane at 2.159 NZ dollars a liter.

Diesel prices were also increased on Tuesday, by 8 cents in Christchurch to 1.60 NZ dollars a liter and by 5 cents a liter to 1.70 NZ dollars in the rest of the country.

The managing director of monitoring company Fueltrack, Chris Kable, said in the short term prices are likely to keep rising, but once uncertainty over issues such as Libya are settled, they are likely to fall rapidly.