A five-year-old boy and three teenagers have been found safe and well, Queensland police say, after an amber alert was issued to find them.

A man — who was known to the children, but was not their father — was allegedly seen dragging the boy into a silver Commodore at Ipswich, west of Brisbane, this afternoon.

A 16-year-old girl, as well as two other boys aged 13 and 17, were allegedly coerced into getting in the vehicle.

Police said at 7:45pm the four children had been located safe and well and thanked the media and the community for their assistance.