Sex crime detectives say the 28-year-old woman had flown to Sydney from New Zealand for business when she decided to meet up with a man she initially met through the dating app on Saturday night.

The woman told police she met the man at a Kings Cross restaurant before going with him to a bar in Martin Place.

After this a number of the man's friends showed up. 

"Later on that night, the woman began to feel dizzy and numb, and lost her bearings," a NSW Police spokesman said.

The woman said she later found herself at a property and had no idea where she was. A number of men then sexually assaulted her.

Police say the woman was eventually able to leave the property on Sunday morning.

She confided in her work colleagues who then informed police. 

After being treated at hospital on Monday, the woman gave a formal statement to police on Tuesday. 

Detectives are confident they will find the woman's attackers but in the meantime want to warn people to be "very careful" when meeting people online.

"The vast majority of people who use dating websites and apps do so for the right reasons, but there are a number of sexual predators out there who use modern technology to find potential victims," Detective Inspector Michael Haddow said.

"We regularly remind people, children and parents in particular, that the use of the internet by sexual predators is an issue they need to be well aware of.

"All those warnings we give to children are applicable to adults."

Detective Inspector Haddow suggested those meeting strangers online should think about bringing a friend along.

"It's absolutely vital that people using dating websites and apps remember that how a person portrays themselves on the internet can be very different from their real life persona," Detective Inspector Haddow said.

"With this in mind, we strongly advise people that if they decide to meet a person they have been introduced to via the internet, then ensure the meeting is in a public place and take a friend along with you.

"Having a friend there ensures that one of you can always keep an eye on your drink, and you have someone to turn to who can help you out should you feel threatened or uncomfortable.

"If it's not possible to bring a friend with you, then, at the very least, stay in regular contact with a family member or friend, keeping them abreast of how the night is going and where you may be heading to."

It is understood the distraught woman has flown home to New Zealand where she is being supported by friends. 

The sexual assault comes two months after a man was charged with murdering a New Zealand tourist he met through Tinder on the Gold Coast in August.

Gable Tostee, 28, is accused of killing Warriena Wright, 26, who fell to her death from the 14th floor of a high-rise on August 8. 

smh.com.au