Kurdish Iranian student Reker Ahmed, 17, was waiting at a bus stop in Croydon, south London, with two friends when they were assaulted at around 11.40pm on Friday.
The Metropolitan Police believes more than 30 people may have been involved in the hate crime. Scotland Yard confirmed on Tuesday that six more people, aged between 15 and 22, have been charged over the attack.
Detectives are also trying to trace the driver and the occupants of a white hatchback with a black roof that stopped at the scene during the frenzy.
Neighbours described how punches and kicks rained down on Reker, who was left in intensive care with a fractured skull and a blood clot on his brain following the assault.
Sixteen people have been arrested in connection with the incident, on suspicion of offences including attempted murder and violent disorder.
Five people charged over the attack appeared before magistrates on Monday afternoon, although police have appealed for information to trace others believed to have been involved.
Two more will appear in court on Tuesday, the Press Association reported.
Addressing journalists at the scene, detective superintendent Jane Corrigan said: “This was a hate crime; there were three individuals who were waiting at a bus (stop) and were viciously attacked.”
She added: “I think this was probably confidence by numbers.
“It started off with this smaller group of people who were joined by between 20 to 30 and they just viciously attacked these individuals because they were asylum seekers.
“We are still seeking the family of the 17-year-old who’s been injured in the attack, but we are providing support to him, his friends and obviously the people who he is in the care of.
“We are also speaking to the school that he attends to see if there’s anything we can offer them by way of support.”
She said Reker, who was identified in court as the main victim, along with friends Dilshad Mohammed and Hamo Mustafa, was being moved out of intensive care after “starting to make a recovery”.
Describing the teenager’s condition, Corrigan said: “Obviously he is going to be scarred for life as a result of the beating he sustained.
“But he is being moved from the intensive care unit into a mainstream ward hopefully later on today.
“His face did receive some significant injuries, that was the main focus of the attack.
“But what I can say is that without a doubt this will leave lasting scars.”
She said police were also investigating whether the attackers had been drinking in a pub near Shrublands Avenue, where the violence took place, an assault she denied was pre-planned.
In an appeal to others caught up in the attack, Corrigan said: “I would prefer the people outstanding in relation to this investigation to make themselves known to us now instead of us making ourselves known to them.
“I am very confident that with the investigation, and the speed with which it has progressed over the weekend, that we will catch all of those involved in this case.”
The assault was condemned as “absolutely despicable” by a visibly angry Theresa May, who spoke to reporters on arrival in Jordan on Monday.
The Prime Minister echoed the comments of local Tory MP Gavin Barwell, who branded the attackers “cowardly and despicable scum”.
Speaking to reporters during a flight to Jordan at the start of a three-day Middle East visit, she said: “This was an absolutely abominable attack, completely unacceptable.
“I absolutely agree with the sentiments of Gavin Barwell when he commented on this and I just hope that anybody who has any information about this will give that information to the police.”