Nationwide, the number of residential property sales in April reached its highest level in six years, with sales up 25 per cent compared to April 2012.
Reinz data showed the national median price eased 2.4 per cent to $390,500, after reaching a record high of $400,000 in March. However, compared to April 2012, the median price jumped $25,500 (7 per cent) year-on-year.
Together, Auckland and Canterbury accounted for 92 per cent of the price increase over the past 12 months.
Ms O'Sullivan said April was notable for a surge in prices and sales of mid-level homes in many parts of the country.
"Several regions appear to be benefiting from the tail-wind generated by the strength of house prices in Auckland and Christchurch."
As house prices continue to soar, the Reserve Bank has warned it will force home buyers to come up with minimum mortgage deposits in a bid to cool the heated property market - sparking concerns that first-time buyers could be locked out of the property market.
Meanwhile, auctions were increasingly becoming the favourite way to sell, with 1368 dwellings nationwide selling under the hammer in April - nearly 20 per cent of total sales.
REINZ data also showed 7104 properties were sold across the country last month, an increase of 1428 sales (25.2 per cent) compared with the same time last year, but a fall of 12.6 per cent compared to March 2013.