CHRISTCHURCH (AFP) - New Zealand police have reopened Dunedin airport after a suspicious package sparked a security alert.

The country is on high alert after a gunman, who is believed to have lived in Dunedin, killed 50 people in two mosques last Friday (March 15).

When a suspect package was found, roads to the airport were closed and Air New Zealand flight 691 from Wellington was forced to circle over the city for almost an hour before being forced to return to its origin.

"Dunedin Airport has reopened after a suspicious item found on the airfield turned out to be a hoax object," police said on Monday.

They said a New Zealand Defence Force ordinance team neutralised the object where it was found.

Inquiries are ongoing to establish who left the object, they said.