Trading was halted on Sydney's leading ASX stock market for almost all of Monday, as operators struggled to fix unspecified "market data issues".

The problems began shortly after trade opened for the week, forcing a market pause as ASX investigated the cause.

Several hours later, the firm said equity markets "will not open for the remainder of today".

"The underlying cause of the issue has been identified," it said, adding that trading should restart on Tuesday's open.

"ASX apologizes for the disruption," a spokesman earlier told AFP.

The cause of the stoppage was not immediately stated, but the outage coincided with a system update which was scheduled to go live Monday – after almost a year of consultations and dress rehearsals.

There was no immediate suggestion of a cyberattack. 

Earlier this year New Zealand's stock market was hit by what was believed to be an overseas cyberattack that disrupted trading for several days.