"It arose from a domestic situation. A man with a pilot's license stole a light plane and threatened to crash into the Sky Tower," Auckland police spokeswoman Phillipa White told The Associated Press. "He's crashed into the harbor ... and emergency services are out there now."
There was no immediate word on the man's condition. He was believed to have been alone in the plane.
At 1,076 feet, Sky Tower is claimed to be the tallest tower in the Southern Hemisphere.
An unknown number of people dining at a restaurant 620 feet up in the tower were evacuated as the drama unfolded.
"It's been cleared but now, security says everything is fine," said customer services manager Sarah Williams.
TV1 said the plane flew close to the Sky Tower after dark, and reported that its pilot had been in radio contact with police.
New Zealand held national elections Saturday, and both Prime Minister Helen Clark and opposition National Party leader Don Brash were due to hold election rallies in Auckland later Saturday night.
TV1 reported that police had arrived outside Clark's house, but it was not immediately clear if they were scheduled to be there because it was election night or to beef up security due to the plane incident.
Clark's ruling Labour party edged slightly ahead in New Zealand's election Saturday, but the race was so close that no immediate decision on whether she would stay in power was expected for days.
Earlier in the evening, New Zealand's opposition leader Don Brash, who supports dismantling the country's nuclear free laws and opposes special privileges for indigenous Maori people, was ahead in the count due to a big swing in support toward his party.
With 95 percent of the votes tabulated, the Chief Electoral office said Clark's Labour Party had 41 percent, while Brash's National Party had 40 percent.
The electoral office forecast that Labour would finish with 50 seats and National 49.
"It's a big swing to the right if it holds up," Labour strategist Pete Hodgson told National Radio.