Using GPS technology, it gathers basic information to match candidates who are most likely to be compatible based on their location.
The head of Auckland's adult sexual assault team, Detective Sergeant James Watson, said the local complaints were very recent and both were being investigated. He could not give further details but confirmed the women said they met their alleged attackers on Tinder.
The Sydney complaint involves a 28-year-old who met a man she connected with on Tinder at a restaurant in Kings Cross on Saturday.
At a nearby bar, they were joined by a number of the man's friends.
Later, the woman began to feel dizzy and numb and lost her bearings. She suspects she was drugged. She told police she found herself at an unfamiliar property where she was sexually assaulted by a group of men.
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Detective Inspector Michael Haddow of the Sydney sex crimes squad said she managed to leave the property on Sunday morning and told work colleagues what had happened. They phoned police. She was treated at a local hospital on Monday and gave police a formal statement on Tuesday. She is back in NZ and being supported by family.
Mr Haddow could not comment further because the investigation was "still in its infancy".
The incidents follow the death of Warriena Wright in August just hours after she met 28-year-old Gable Tostee through Tinder. Tostee was charged with murder after Ms Wright, a Kiwi in Australia for a wedding, fell to her death from his Surfers Paradise high-rise apartment.
He is due back in court tomorrow.
Mr Watson was not aware of the alleged gang rape in Sydney at the weekend, but said police here could be contacted by Australian colleagues to help with support and counselling for the victim.
He said people, especially women, needed to be careful when meeting in person contacts they had been introduced to online.
"Women need to be very aware of who they are meeting when they are alone and without their friends."
NetSafe executive director Martin Cocker said the number of complaints around online dating, meet-up sites and apps was "slowly growing" and users needed to remain vigilant about safety.
"Criminals are using them to meet people - that's clear. Whether they go from bar to bar looking for drunk people or scroll through their apps, either way they are doing it to commit a serious criminal act."
Offenders used online and dating apps for the same reason people searching for love joined them.
HOW TO STAY SAFE
If you are meeting someone you have been introduced to online:
• Take a friend
• Meet in a public place
• Keep an eye on your drinks
If you go alone, stay in regular contact with a friend or family members so they know how and where you are.
