A group of children, some as young as nine, are pretending to be asylum seekers to steal bags and valuables.
A police spokesman said: "They are going up to people sitting outside cafes in the city centre to beg for money.
"Some distract the victims while accomplices steal handbags and mobile phones left on tables.
"They say they are asylum seekers but we are convinced they are local lads, aged between nine and 14."
The spokesman warned everyone to be on guard. He said: "Keep hold of valuables at all times."
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