A seven-year-old boy was airlifted by police helicopter to hospital with serious injuries after a head-on smash on the notorious A31.

The youngster from Upton, in Poole, had to be cut free from the back seat of a Mitsubishi car full of his family following the collision involving a Vauxhall Zafira.

It happened near the Roundhouse roundabout at around 11.40am yesterday.

The Vauxhall driver, a Ferndown man in his 30s, was also flown from the scene, by Dorset Air Ambulance.

Both casualties are being treated for serious injuries at Dorset County Hospital in Dorchester.

PC Chris Wales, of Poole’s traffic department, pictured right, said at the scene: “Two people have been airlifted by Dorset and Somerset Air Ambulance and the Dorset Police helicopter.

“They are serious but stable and their injuries are not thought to be life threatening. The seven-year-old boy was in the rear seat of the Mitsubishi, and the other four people in his car are basically walking wounded.

“They have all gone to hospital.” The road was closed in both directions for several hours, between A350 Poole Road, Roundhouse Roundabout at Sturminster Marshall and the B3075 World’s End Pub, Winterborne Zelston.

Firefighters removed the black Mitsubishi Warrior’s roof to free the boy and another backseat passenger, PC Wales added.

A 50-year-old woman and a 56-year-old woman were taken to Poole Hospital for treatment.

The car, carrying the boy and four adult members of his family, had been travelling towards Bere Regis when it was involved in a collision with the grey Vauxhall, coming the other way.

“We already have some witnesses to the crash but will be appealing for more,” PC Wales said.

“As it’s a Bank Holiday weekend there was a reasonable traffic volume at the time and the more witnesses we have the better.”

The boy is thought to have sustained abdominal fractures while the man was treated for possible broken arm and collar bones.

Tracy Bartram for Dorset and Somerset Air Ambulance said: “We had two paramedics at the scene and they spilt into two so that each could accompany one of the casualties.”

Both vehicles were recovered from the scene, a few hundred metres down from the Dullar Lane junction, and the road re-opened shortly before 4pm.

Witnesses or anyone with information should call PC Chris Wales on Dorset Police on 101.