Police said that a group of about 20 people was involved in the attack on the 17-year-old in the Croydon borough of southeast London, which they said was being treated as a hate crime.
The Press Association reported that the teenager was a Kurdish Iranian and suffered a fractured skull and a blood clot on his brain. Police have not identified him.
Police arrested nine people, ranging in age from 17 to 26, over the weekend and another person on Monday in connection with the attack.
Four people were charged with violent disorder, and one with violent disorder and racially aggravated grievous bodily harm, police said Monday. Those charged are all in their twenties, police said.
The Metropolitan Police said they were called to the scene at 11:40 pm local time Friday. Detectives believe a group of suspects approached the victim as he waited with two friends at a bus stop outside The Goat pub.
Detective Inspector Gary Castle of Croydon's criminal investigation department said in a statement Monday: "We now know that a large number of people, approximately 20, were involved in the attack on the victim."
He added that the teenager sustained serious head and facial injuries as a result of the attack, "which included repeated blows to the head by a large group of attackers."
Addressing reporters at the scene Monday, Detective Superintendent Jane Corrigan said: "I'm absolutely delighted to say that the 17-year-old boy that was injured in this vicious attack is actually starting to make a recovery and we are hoping that he is going to move from the intensive care unit to a main ward, where we will obviously be seeking to support and ask him about this incident."
One resident told the Press Association: "There was a group of roughly 10 people that was kicking and punching him, and the rest, another 10 or 20, were all just around watching. Then when they heard sirens they started to go."
A crowdfunding page
has been set up to help the victim "overcome this horrible ordeal and show that he is loved and welcome here in the United Kingdom."
The page had raised almost £6,000 (about $7,500) by Monday afternoon, with hundreds of well-wishers leaving messages expressing support for the young man.
Bridey Watson, 35, told CNN she set up the page after hearing about the attack.
"I have been bowled over by the response, such messages of kindness. I think this has shocked the whole nation and everyone wants to stand up and say 'no, this is not what we're about'," she said.
Watson said she is working with a youth and refugee worker to ensure the young man benefits from the fundraising effort without it affecting his asylum claim.
London Mayor Sadiq Khan posted a statement on Twitter saying: "Hate crime has no place in London, Britain or anywhere else."
Jeremy Corbyn, leader of the opposition Labour party, also condemned it: "Absolutely shocked at attack on young Kurdish asylum seeker, who came here searching for safety. I fervently hope he makes a full recovery."
According to the Refugee Council, 30,603 people applied for asylum in the UK last year. Of these, 2,666 were from Iraq, which was the third biggest source of asylum-seekers behind Iran and Pakistan.