Kingston police have arrested a further six people in connection with a vicious assault in Blagdon Park, New Malden which has left a 16-year-old boy fighting for his life for the past two weeks.

A total of 11 people have now been arrested and bailed until May 19.

The teenage victim, who is yet to be named, has been kept alive on a ventilator at the Atkinson Morley wing of St George’s Hospital, Tooting, after suffering life threatening head injuries during the attack on April 8.

Witnesses said a gang of up to 20 youths took part in the daylight assault, punching, kicking and jumping on the victim’s head before escaping on the 152 bus towards Pollards Hill.

DCI Jez Clarke, the officer leading the investigation, said he had never seen such an appalling, violent attack.

He said: "They seem to have grabbed mobile phones, speakers, that sort of thing, but I have no idea what led to the sustained level of violence.

"We’ve had reports that they were acting very aggressively and rowdily.

"Did you see them on the train or in the New Malden High Street before the attack?

"Where did the rest of the group go?"

Members of staff from the nearby Malden Centre have been praised by onlookers for racing to aid the critically injured teenager, providing essential first aid while they waited for the ambulance to arrive.

One witness described how the centre’s duty manager waited with the boy, holding him and stroking his hand to calm him down as he drifted in and out of consciousness, while another said fellow centre staff who rushed to help the boy had been left traumatised by the injuries they saw.

Kingston police are continuing their appeal for witnesses to the attack, which happened at about 7.30pm.

Anyone with information can contact Kingston CID on 020 8247 4909, or Crimestoppers anonymously on 0800 555 111.