The emirate is now home to the highest concentration of billionaires in the region - there are 14 of them -- and ranks 18th globally, fresh data from WealthInsight, which analysed more than 1,300 billionaires, showed.

New York was ranked as the city with highest number of billionaires, followed by Moscow, London and Hong Kong.

"In terms of competition with Dubai, it has more to do with the Indian business," Stephen Gross, a senior analyst in WealthInsight, was quoted as saying by The National newspaper.

The UAE has a number of foreign national billionaires in the country, coming from countries including Bahrain, India, New Zealand, Pakistan and Saudi Arabia.

"There's a lot of Indians who are not residents in India, and those are the ones that Dubai and Singapore are both competing for. Both locations are also courting billionaires seeking a haven from having to pay taxes, particularly after scrutiny increased over accounts in Switzerland."

"Dubai could benefit from wealthier individuals coming into the emirate following the Arab Spring, and if more unrest in the region continues -- but there had not been such an effect among billionaires as of yet," Gross said.

Since 2007, the average per-capita wealth of billionaires residing in the UAE has dropped 10 per cent, though the number of billionaires has doubled, WealthInsight said.

Singapore stands to gain the most from a growing group of billionaires who hail from China, which has five cities in the top 25, including Shanghai in 8th spot.

Dubai, two other Middle Eastern cities -- Jeddah and Riyadh -- also made it into WealthInsight's top 25 ranking.

Istanbul, which is considered neither a part of the Middle East or Europe by WealthInsight, took sixth spot, ahead of San Francisco but just behind Mumbai.