A New Zealand airport has imposed a three-minute limit on farewell hugs, sparking a worldwide debate over how long to cling on for a cuddle.

Bosses at the international airport in the southern city of Dunedin say they were surprised by the viral response to their new rule in the car drop-off zone.

"To keep things moving smoothly, we've installed new signage, including the 'Max hug time 3 minutes' sign," said airport chief executive Daniel De Bono.

"It's our way of being a little quirky and reminding people that the drop-off zone is for quick farewells," he said.

"And don't worry – just a 20-second hug is enough to release oxytocin and serotonin, the happy hormones that boost well-being, so three minutes is plenty of time to say goodbye and get your dose of happiness."

People who want a longer hug can use the car park, where the first 15 minutes are free, he said.

The hug restriction made headlines worldwide and prompted a divided online response.

"I'm just glad there's no minimum hug time. A 'see ya soon' suffices," one woman commented on the airport's Facebook page.

"Hug Police!? This is just weird! Hugs are proven to have many benefits not to mention mental health," said another poster.

The airport said it started the hug limit in September with little initial reaction. 

"We have just been surprised how much global interest there has been," said the airport's marketing and communications executive, Sarah Soper.