Luanda, Angola's capital, for the second year in a row. This is according to the 'Worldwide Cost of Living Survey 2011' carried out by HR consultants Mercer.

According to the survey Tokyo is the second most expensive city for expats, and N'Djamena, in Chad, the third. Europe is represented on the fourth and fifth place by Moscow, Russia and Geneva, Switzerland.

Mercer includes 214 cities across five continents in the survey and compares the cost of more than 200 items in each city, including housing, transport and food.

Like in other African cities the main expense placing Luanda in first place is record accommodation prices. According to the report the cost of renting a luxury two-bedroom unfurnished apartment is an average of $7,000 per month. Compare this to $4,300 in New York, $3,345 in Shanghai, $2,456 in Rome and $1,800 in Buenos Aires.

"Finding good and secure accommodation for expatriate employees is a real challenge in most of the African cities on the list and costs can be significant compared to other regions. Accommodation prices are currently at record levels in cities like Luanda and this is generally the main reason why we find so many African cities high up in the ranking," Mercer senior associate Nathalie Constantin-Metral explains in a press release.

You can study the full list of ranked cities here