A man is in critical condition in hospital after crashing during a police pursuit in Wigan.
The man in his 20s had been riding an off-road moped.
He failed to stop shortly before 4.45pm on Sunday, Greater Manchester Police said.
Officers, who had been taking part in an anti-social behaviour operation, were chasing him while riding off-road bikes.
The man came off his bike on Shuttle Street in Tyldesley and was taken to hospital in a critical condition.
The incident has been referred to the Independent Office for Police Conduct.
PC John Cavanagh, from GMP's serious investigation collision unit, said: "Our thoughts are with the man's family who are understandably distressed whilst he fights for his life in hospital.
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"A cordon is currently in place at the scene and we have referred the incident to the IOPC due to the police contact in the moments before this incident.
"We will do all we can to support any subsequent investigation."
Anyone with information can report it online or by using LiveChat at www.gmp.police.uk quoting incident number 2138 of 06/06/2021. People can also contact Crimestoppers anonymously on 0800 555 111.