Five children have suffered minor injuries hurt after a jumping castle blew away in Sydney.

The device detached and blew over a fence next to where it was tethered in Kelvin Park Drive, Bradfield near Liverpool.

Emergency services were called at 9.35am.

Three nine-year-olds, as well as a 12 and 13-year-old were assessed by NSW Ambulance paramedics for non-life-threatening injuries, they said.

They were taken to hospital in stable conditions.

SafeWork NSW are there, NSW Police said.

According to the BOM, wind gusts of up to 74km/h have been recorded in nearby Canterbury, and 89km/h at Sydney Airport.