A three-year-old boy has died after he was in collision with an articulated lorry as he crossed the road on a pedestrian crossing, police said.
The boy was crossing North Street in Wareham, Dorset with his family on Thursday morning when he was struck by a Sainsbury's lorry.
The toddler, who has not been named, sustained very serious injuries and was taken to Dorset County Hospital for treatment but was pronounced dead a short time later.
Dorset Police said a 43-year-old man from Basingstoke has been arrested on suspicion of driving offences and is assisting officers with their inquiries.
Inspector Matt Butler, of the force's traffic unit, said: "Very sadly I can confirm that a three-year-old boy has died today following a collision.
"Our thoughts are with his family and friends at this very traumatic time. They have requested privacy.
"A full investigation is under way into the circumstances of the collision and I would ask anyone who witnessed the incident or saw the manner of driving of the lorry immediately before to please come forward.
"I am also keen to hear from any motorists who were travelling along North Street at the relevant time and have dashcam fitted in their vehicles."
North Street has been closed between the junction with West Street and the roundabout at the junction with the A351 while collision investigators examine the scene.
The Dorset Coroner has been notified of the boy's death, police added.