BUSINESSDESK: New Zealand house sales and prices rose last month on the continued strength of the Auckland and Canterbury property markets, Real Estate Institute figures show.

The number of sales rose 24% to 7175 in May compared to the same month a year ago, and was up from 5676 in April, the institute said.

The national median sale price rose 5.4% to $369,000, and was up $4000 from a month earlier.

The REINZ stratified house price, which irons out peaks and troughs in pricing information, rose 1.7% to 3390.6, and is up an annual 6.4%.

"The increase is considerably stronger than normal seasonal trends would suggest," president Helen O'Sullivan said. "The strength of the real estate market continues to be focused on Auckland and Canterbury."

Tight Auckland and Christchurch housing supply has been cited as the cause of a rebound in the property market over the past year, as growing demand outpaces a shortage of new listings and new construction remains light.

The number of sales in Auckland climbed 28% to 2792, while the median sale price rose 7.8% to a record $500,000 from May 2011. Canterbury sales surged 56% to 1021with the median price rising 8.8% to $335,000.

ASB economist Jane Turner said the "underlying trend in housing market turnover is one of gradual improvement", with low interest rates likely to stoke demand.

"The Reserve Bank is expecting to see around 5% annual house price inflation over the coming year (on the more stable quarterly QV house price index), although with momentum continuing to build the risks are house prices growth faster than this," she said.

The number of sales in Wellington climbed 28% to 735 in May from the same month a year earlier, though the median sale price was down 1.7% at $368,750. Dunedin sales rose 7.8% to 179, with the median sale price falling 2.6% to $250,000.

The institute said the national median time to sell rose to 38 days from 37 days in April, but was seven days faster than a year earlier.