Twenty people have been killed in a crash involving a limousine transporting a wedding party in the US state of New York, police say.

All 18 people in the limousine died along with two pedestrians in the incident on Saturday afternoon in the town of Schoharie, police confirmed.

Eyewitnesses described seeing an SUV-style stretch limousine leave the road and plough into people at a store and cafe near a busy intersection.

The cause of the crash is unclear.

State police said on Sunday that passengers travelling in the limousine, described as a 2001 Ford Excursion, would not have been required to wear seatbelts.