Police are warning online daters to be careful of meeting with strangers after a tourist was gang-raped after being introduced to a man she met on mobile dating app Tinder.

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 says she was at a bar in Martin Place when her date's friends showed up. Credit:Louise Kennerley

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.