Even million-dollar properties are not immune from a slowdown in Auckland, new data from the Real Estate Institute says.

The number of properties sold nationwide for more than a million dollars dropped 4 per cent in the first half of this year compared to the same six months of 2016.

That change was due to the Auckland market. In the country's biggest city the number of million-dollar property sales fell 8 per cent. Across the rest of the country, excluding Auckland, the number of million-dollar sales increased 16 per cent.

"Even at the top end of the market we're starting to see signs of stabilisation occurring – in part due to loan-to-value ratios continuing to have a greater impact on people's ability to purchase property but also due to the fact buyers will be starting to take into account interest rate predictions over the next 12 to 18 months as this will have a significant impact on how people structure their mortgages when purchasing these high-end properties," said chief executive Bindi Norwell.

"When you look at the Auckland picture, [the first half of 2017] saw the lowest number of million-dollar plus properties sold in Auckland since [the second half of 2014] – a clear nod to the stabilisation of property prices in New Zealand's biggest city. However, most regions saw the top end of the market grow highlighting the buoyancy we're experiencing around the country."

Otago had the third-highest number of properties for sale for more than a million dollars. Hawke's Bay, Nelson, Taranaki, Tasman, Waikato and Wellington all had record numbers of million-dollar sales in the first half of this year.

There were 241 sales for more than $3m, of which 213 were in Auckland. Another 56 sold for more than $5m, 51 of them in Auckland.

Norwell said it was likely that other parts of New Zealand would start to see more million-dollar property sales, as Auckland had.

She said the work agents had to do to sell a $3m or $5m property was different to that for a median-priced home. She said buyers often had more specific requirements in what they were looking for and agents would run a different sort of campaign.

Manawatu had its first $5m-plus sale in the first half of this year, in the Ruapehu district.

$1m+ plus sales, first half of 2017:

Auckland: 4129

Bay of Plenty: 180

Canterbury: 166

Gisborne: 2

Hawke's Bay: 30

Manawatu-Wanganui: 6

Marlborough: 7

Nelson: 17

Otago: 182

Southland: 2

Taranaki: 16

Tasman: 22

Waikato: 138