A man was assaulted as he tried to recover his stolen bike - then had a second bicycle taken.
Police are appealing for witnesses to the assault and theft in Hull just before 5pm on Monday to come forward.
A Humberside Police spokesperson said: "At around 4.50pm a man was riding his bike along Buckingham Street when he saw someone with a bike which had been stolen from him outside a shop a few days before.
"He challenged the person with the stolen bike but was then assaulted by another man who arrived at the scene in a black Peugeot 206.
"The bike that the victim was riding was then also stolen from him."
Witnesses should call the police on 101.