A man has been arrested on suspicion of two counts of attempted murder after detectives linked two incidents where men were set alight in Birmingham and London, the Metropolitan Police said.
Mohammed Rayaz, 70, was set on fire on his way back from Dudley Road Mosque in the Edgbaston area of the city at about 7pm on Monday.
He remains in hospital with severe injuries.
Police say it is linked to a similar attack on a man walking back from West London Islamic Centre in Ealing on February 27.
The suspect was arrested on Tuesday on suspicion of the attempted murder of Mr Rayaz.
He was later arrested on suspicion of the same offence following joint inquiries by West Midlands Police, which is leading the investigation, and the Met.
Detectives from both forces are working to establish the full circumstances.
Chief Superintendent Sean Wilson, of the Met’s west area command, said: “We completely understand the shock that resonated throughout the community following this incident.
“Despite a man having been arrested, we continue to be vigilant and urge local people to do the same.
“Highly visible patrols around Singapore Road will continue in the coming days to provide reassurance to local people and I urge anyone who is concerned to approach officers.”
During the London attack, the suspect and victim spoke for around five minutes before the suspect allegedly doused the victim in a liquid, believed to be petrol, and then set him alight using a lighter, according to police.
The suspect then allegedly walked away and the victim was taken to hospital where he was treated for severe burns on his face and arms.
Counter-terror police are supporting the investigations.
Officers are keeping an open mind as to any potential motive at this stage.
Anyone with information can call West Midlands Police on 101 or independent charity Crimestoppers, anonymously, on 0800 555 111.
Anybody with relevant CCTV, dashcam, ring doorbell or video footage has been urged to send it via https://mipp.police.uk/operation/20HQ23C02-PO1.