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Kiwis with a taste for posh hamburgers are tucking into a new gourmet range from Burger King, and now the chain's international bosses are looking to take a bite.

The company's headquarters in Miami are taking a close interest in promising sales of the Crown Jewels range, which was developed in New Zealand.

Tasman Pacific Foods, which operates Burger King in New Zealand, says it is reporting regularly to corporate HQ about the new range, which includes the Hell Raiser, Sweet Ride and Blazing Saddle beef burgers.

Less than two months after becoming a permanent part of the menu, the new burgers are delivering more than 10 per cent of sales.

Burger King New Zealand general manager Glenn Corbett says that the results had been encouraging and that the corporate office in Miami was "extremely interested" in how it performs over the next two months.

The project was developed after sales research for the New Zealand operation.

Glenn Corbett says the burgers developed here are for New Zealand tastes and would likely be adapted to different markets around the world.

The Crown Jewels range has been developed over the past 12 months, giving Burger King New Zealand a taste for the premium end of the fast food market.

The same company last month bought the franchise for the premium fast food Hell Pizza brand.

Marketing positioning statements for Crown Jewels are direct.

Advertising says the burgers are "flash, but not too flash".

In other words they cost more than your standard burger but not as much as you would pay at a gourmet outlet.

The range typically costs $1.50-$2 more than the standard Whopper combo.

"Ingredients for the range include mango lime salsa, avocado, garlic aioli - not the kind of ingredients you would typically expect to find at one of the multinational fast food chains," Burger King says.

As well as the beef burgers the range includes three premium chicken burgers: Blast Off, Cracker Jack and Mango Jammin'.

"We wanted to give the idea of exclusivity. We are saying here is something indulgent but you can afford to pay for them," Corbett says.

The head of the gourmet Burger Fuel franchise, Chris Mason, acknowledged the arrival of a multinational into the gourmet burger market but said it does not represent a threat to the 16 outlets in its franchise.

"Burger King say 'gourmet' but I don't think they are fooling anybody - we've tried them and they are okay."