LONDON -- UK detectives appealed Saturday for information and witnesses who might have seen a group of youths attack a teenage asylum-seeker in the London borough of Croydon.

The attack left the 17-year-old Iranian Kurd in serious but stable condition in a London hospital. Authorities are treating the matter as a suspected hate crime.

Detective Sergeant Kris Blamires said the teenager was at a bus stop with two friends when approached by about eight youths.

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“The suspects asked the victim where he was from and when they established that he was an asylum seeker they chased him and launched a brutal attack,” Blamires said in a statement. “He has sustained serious head and facial injuries as a result of this attack, which included repeated blows to the head by a large group of attackers.”

The teen’s friends managed to get away.

British police say hate crimes remain under-reported in Britain. The country has seen a surge in xenophobia expressed in threats, taunts and physical attacks after Britain’s vote to leave the European Union last year.

Much of the Brexit debate focused on an influx of migrants into Britain from other EU countries - and whether their presence was making it harder for Britons to find work, housing and medical care.

Police recorded 1,546 racially or religiously aggravated offenses in England and Wales in the two weeks before the June 23 referendum, and 2,241 in the two weeks after it, the Home Office said. The total for July was up 41 percent from the same month a year earlier.

London’s police force has increased the number of specialist investigators by 30 percent in the past two years, with more than 900 dedicated to investigating such attacks.