Oslo, Zurich and Tokyo are the world's most expensive cities, but it is in the Swiss financial capital that residents enjoy the strongest purchasing power, according to a study published Friday.

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These three cities are the most costly on the planet when comparing prices for 122 goods and services, according to Swiss bank UBS, which carried out the analysis of purchasing power in 72 cities around the world.

"When rents are added to the mix, New York, Hong Kong and Dubai jump up in the list," the bank pointed out.

Not counting rents, New York is only in sixth place, Dubai ranks 22nd and Hong Kong 32nd.

The Indian cities of Delhi and Mumbai meanwhile have the lowest cost of living, the study showed.

These two cities also bring up the rear in terms of gross salary levels, with workers there on average receiving just six percent of the average wage in list-leader Zurich.

Geneva, another Swiss city, comes in second in the salary ranking, followed by Copenhagen, UBS said, adding though that after tax the Danish capital is bumped by Luxembourg.

Workers in Oslo, which according to the study is the world's most expensive city, meanwhile enjoy the fourth highest wages on the planet.

Zurich is also a winner in terms of purchasing power, with the net hourly wage in the city buying the most goods and services, UBS said.

"Workers in Zurich can buy an iPhone after 22 hours work. In Manila, by contrast, it takes around 20 times longer," the bank pointed out.