A woman has been rushed to hospital after a BMW sedan slammed into outdoor diners at a Sydney cafe before the driver allegedly fled the scene.

Emergency services rushed to a cafe on Norton St in Leichhardt on Saturday morning after the vehicle crashed outside the venue, seriously injuring one woman who was pinned by the car.

The woman, aged in her 70s, was rushed to hospital in a serious condition, with others assessed by paramedics.

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The driver allegedly left the scene.

A short time later, officers tracked down the BMW and arrested the driver — a man in his 30s — who was taken to the same hospital under police guard for assessment.

An investigation into the circumstances surrounding the crash is now underway.

A woman has been taken to hospital in a serious condition.A woman has been taken to hospital in a serious condition. Credit: 7NEWS

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