Some protesters were seen stealing motorbikes which they set on fire along in the street. At times police struggled to maintain control as the fires continued to burn.
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The families of all four of the victims, all of whom were men, have been informed, police said.
A motorcyclist from Nottingham has died in an accident at the Macau Grand Prix in China, earlier today.
AC/DC co-founder and ex-guitarist Malcolm Young has died aged 64, his publicist has announced.