You've thought about investing in property in London or Hong Kong, but what about Istanbul or Melbourne, Australia? CNBC takes a look at which housing markets across the world posted the biggest gains in 2015 and which ones you should watch next year.

The data are predominately based on property consultancy Knight Frank's most recent Global House Price Index, published at the end of last month, which tracked prices until the end of September. It is based its data on official government or central bank statistics where available.

— By CNBC's Katy Barnato
Posted 30 December 2015

House prices in Australia rose by 9.8 percent in the 12 months to September, according to Knight Frank, which said this was one of the fastest rates in the world.

However, the increasing unaffordability of housing and the introduction of fees for foreign investors purchasing new builds from December 2015 is likely to mean the country moves out of the top-10 strongest risers in 2016, the global real estate agency told CNBC.

After London and Hong Kong, Sydney was singled out by UBS as the world's most overvalued city in its Global Real Estate Bubble report in October.

House price growth in Canada continues to eclipse that of the U.S. In the 12 months to September, home prices rose by 5.6 percent, trumping growth of 4.9 percent in the U.S., according to Knight Frank.

Property values in major Canadian cities like Toronto and Vancouver have soared, partly due to record-low interest rates making mortgages more affordable.

However, a growing number of investors are betting the market will crash, as low energy prices weigh on the country's economic outlook, according to market research firm Markit.

House prices in Hong Kong, a special administrative region of China, rose by 16.7 percent in the 12 months to September, according to Knight Frank. UBS said in October that Hong Kong was the world's least affordable city to buy real estate in and the second most likely after London to suffer a property bubble.

Knight Frank told CNBC in December that the Hong Kong housing market could be hit in 2016 by rising interest rates in the U.S., given that the city-state's currency is pegged to the U.S. dollar.

However, it forecast that house price gains would remain strong until the end of 2015, ensuring that Hong Kong stayed in the top-five countries for property price growth in the fourth quarter.

Longer term, China's economic slowdown could start to weigh on Hong Kong's housing market, as wealthy Chinese grow wary of making further investments or look further afield to do so.

House prices rose by an average of 8.9 percent in Ireland in the year to September and the market looks set to improve further, Knight Frank told CNBC. Home prices in the country, which was hit hard by the global financial crisis, remain 34.6 percent below their pre-crash peak, according to the real estate agency.

House prices in counties like Longford, Westmeath and Donegal only bottomed out in early 2014, while prices in Limerick did not hit their lowest until the end of last year, according to Irish property website, daft.ie.

House prices in Israel kept on rising due to limited supply, but the rate of increase slowed this year and is seen decelerating further in 2016.

Nominal home price growth read 5-6 percent in 2015, down from 7.8 percent in 2014, according to Standard & Poor's. The ratings agency says that house price growth will slow further to 3.5 percent next year and 2.5 percent in 2017, due to predicted mortgage rate increases.

"We think that the Bank of Israel may raise its main policy rate toward the end of 2016. … However, we think that the current shortage of supply will likely offset to some extent the effects of mortgage interest rate rises on house prices," S&P said in a report last week.

It forecast that 50,000 homes would be built annually in 2015 and 2016, but that this would be insufficient to counter the housing deficit.

House prices in New Zealand leapt by 12.6 percent in the 12 months to September, according to Knight Frank. The real estate agency said that home prices in the country stood at 43 percent above their financial crisis lows.

New Zealand Prime Minister John Key discussed with CNBC the problem of soaring house prices in Auckland, the country's most populous city.

"House prices doubled under the previous government and they've gone up pretty similar numbers under us," he told CNBC in October.

"The population's growing reasonably rapidly; there have been supply issues, so we're doing a lot of different things. We're building a lot of houses. So to give you an example, we've got the highest consent rates and building rates for a decade, but we're building three times as many houses as we did say seven years ago when I became PM."

Property prices have risen fast in Scandinavia this year, with Norway recording gains of 6.1 percent in the year to September, according to Knight Frank.

When S&P reaffirmed Norway's triple-A credit rating in October, it warned that "a potentially rapid correction in real estate prices constitutes an economic vulnerability that could dampen growth considerably through weakened consumption and a further falloff of investment activity."

House prices in Singapore declined by 4.3 percent in the 12 months to September, Knight Frank said, based on an islandwide price index for nonlanded homes, where the property has no accompanying land.

The drop comes as economic growth moderates in the country and is a result of a deliberate policy by the government to slow the overheated housing market. Measures taken include capping the tenure of residential loans at 35 years and increasing the stamp duty (the tax paid on purchases of property or land).

Sweden was Europe's strongest-performing housing market in the year to September, according to Knight Frank. Prices rose 11.1 percent year on year in part due to undersupply, according to provisional data.

"Demand is outpacing supply with household borrowing having risen at twice the rate of economic growth since 2009," the real estate agency said.

In December, S&P said that the climb in housing prices and high household indebtedness in Sweden posed risks to its banking sector and covered bond market. The ratings agency added, however, that the Swedish state would likely step in to support covered bonds if necessary. Covered bonds are debt instruments secured by a pool of mortgages or public loans.

House prices in Turkey leapt 18.9 percent in the 12 months to June 2015 (the latest date for which data were available), according to Knight Frank.

"Strong levels of foreign investment, an expanding population and a slowdown in construction explain the upward pressure on prices," the real estate agency said in its report.

Knight Frank told CNBC that the country would likely hold onto its ranking in the global top-five countries for house price growth in the latter part of 2015.

Turkey's population has been inflated by an influx of refugees and migrants this year. There are 2,291,900 registered Syrian refugees in the country, according to the United Nations.

Prices for "mainstream" U.K. houses grew by an average of 4 percent in in 2015, varying between 2 percent in Scotland and the northeast of England and 8 percent in London, according to Savills.

The real estate agency sees house price gains across the U.K. accelerating to 5 percent in 2016, with prices 17 percent higher by the end of 2020.

Mainstream refers to the bulk of the U.K. housing market, as opposed to prime, which is usually the top 5 percent of the market by house price.

"Much depends on the speed at which interest rates rise," Lucian Cook, head of Savills residential research, said in a report last month.

"If rates rise too quickly, mainstream house price growth will be quickly curtailed. On the flipside, if rates remain low for too long, there is a risk that prices will rise too far, creating affordability issues further down the line when they do eventually rise."

UBS warned in October that London was the most overvalued city for real estate in Europe and the most at risk in the world for another housing bubble.

House prices in the United States rose by a moderately high 4.9 percent in the 12 months to September, according to Knight Frank, which told CNBC that this rate could slow heading into next year.

"The Federal Reserve rate rise (on December 16) won't impact fourth-quarter data, but we expect the U.S. and some markets pegged to the U.S. dollar (Hong Kong and many emerging markets in the Middle East, Caribbean and Latin America) will see the rate of growth start to slow (particularly in those markets where a high volume of new supply is due to be delivered in 2016)," Knight Frank told CNBC earlier this month.