A New Zealand zookeeper has been killed by a Sumatran tiger on a weekend morning that the zoo was open to visitors.

Police said they were called to the Hamilton Zoo at 11 a.m Sunday after reports a female zookeeper had been attacked by one of the zoo's five tigers. Police said the woman died at the scene.

The incident prompted the zoo to ask all visitors to leave and close its doors until Thursday.

Police said authorities are investigating to determine exactly what happened.

Zoo visitor Adam Rich told The New Zealand Herald newspaper he saw the tigers about 45 minutes to one hour before the zoo was evacuated and noticed a zookeeper opening up a gate to allow the tigers access to an outdoor area.