A dog has attacked three people including two young children, leaving one of them with life-threatening injuries.
The other child was left with life-changing injuries, Essex Police said.
Officers were called to the junction of Tara Close and Harwich Road, Colchester, at 15:10 BST after reports someone had been bitten by a dog.
Paramedics treated the two children at the scene and they were taken to hospital along with a third person.
The dog has been “recovered by police”, a spokesman said.
The East of England Ambulance Service said it sent three ambulances, a rapid response vehicle and an ambulance officer alongside an air ambulance.
A property on the corner of the two roads remains cordoned off.
A neighbour, who wanted to be known only as Rachel, said the events were “quite frightening”.
“Having an 18-month old myself, I think it’s quite scary that a dog can do that.
“Someone from the police has been and knocked and asked if I know who lives there. It’s quite scary, to be honest, especially when it’s on literally your doorstep.
“I feel really sorry and my heart goes out to the people involved in it.”