Emergency services were called to Stock Road in Stock, south of Chelmsford, just after 8.20am on Friday.

The second child was taken to hospital for treatment. The children's ages were not immediately released.

A 23-year-old man has been arrested on suspicion of causing death by dangerous driving, causing serious injury by dangerous driving and driving whilst unfit through drink or drugs.

The road remains closed between School Lane and Honeypot Lane.

Detective Inspector Mark Fraser, of Essex Police's serious collision investigation unit, said: "This is quite clearly an incredibly tragic incident which will be felt by many people across the area, not least the families of the two young victims.

"Our role is to establish the circumstances which led up to this incident, which we will do meticulously, and I would ask people not to speculate, whether in person or online.

"I would also like to thank everyone who has already come forward to speak to us and would urge anyone who has information and not yet spoken to us to please come forward."