Wellington, New Zealand - The main highways into New Zealand's main cities were brought to a virtual standstill on Friday by truck operators protesting a sudden rise in road fees.

Hundreds of trucks, with horns blaring and trailing banners, clogged the main roads into the capital, Wellington, and the country's largest city, Auckland, at the height of the morning rush, reducing commuter traffic to a crawl.

The truck operators, already under pressure from a surge in oil prices, took the unprecedented action in response to a government decision to raise road user charges by an average 7.5 per cent earlier in the week without advance warning.

Truck operators said they had been promised at least one month's notice of any increase.

New Zealand Transport Minister Annette King said she had asked a committee to look into the formula used to set road user charges.

'There is no doubt that there is dispute on both sides of the argument as to the accuracy of the formula used to set the charges,' she said in a statement.

She said the last time advance warning was given, truck operators bought large amounts of the charge vouchers ahead of the price rise effectively depriving the government of NZ$17 million (S$17.48 million) in revenue.

The road user charges are levied on diesel-powered vehicles or trucks weighing more than 3.5 tonnes.

The truck operators claim that the increase in fees are another burden for a sector struggling to cope with record high fuel prices.

Protests have spread across Europe and Asia as oil has hit record highs on world markets.

Truckstops across India were at a standstill on Thursday as truckers nationwide staged a strike over rising fuel bills, while in Australia, truckers clogged a commuter freeway earlier this week, also in protest against rising fuel costs. -- REUTERS