Trading was down on the share market for much of yesterday as the NZX struggled with technical issues.

Trade had been suspended since 11.15 yesterday morning, although is expected to resume today.

Reuters sent an alert to clients that NZX equities and indices data wasn't updating due to an issue at the exchange, affecting all vendors.

NZX chief financial officer Graham Law said in a statement yesterday afternoon that the incident with trading in the markets experienced was due to an "internal operational issue", which was being further investigated.

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"We can confirm that this was not due to a technical issue in the NASDAQ trading system," he said.

"Following the resolution of the initial issue, a secondary issue has arisen which has resulted in further delays, NZX is currently investigating," he said.

The outage comes at a busy time for the market as the end of the reporting season draws near.

"You do need these things to work efficiently," Harbour Asset Management portfolio manager Shane Solly. "It's a tough time to be down," he told the Herald.

The exchange had been in regular contact with market participants throughout the period. NZX's current focus is on recommencing trading as soon as possible.

The stock market operator introduced the Nasdaq platform in 2014, letting it branch into new securities trading such as derivatives and commodities. The platform has faced intermittent issues, most recently with an outage last year.

NZX is spending more time on its core market function, putting it at the heart of a strategic overhaul last year. That includes a new pricing structure set to start in October.

The benchmark S&P/NZX 50 index edged up 0.1 per cent to 9,214.02 before the glitch stopped trading on turnover of $16.5 million.