Organised criminal gangs are operating "bag-dipping rings" in the city centre as shoppers hunt down sale items.
Bag snatchers and pickpockets are often part of a network of gangs and serious and organised crime groups.
With around 100,000 people descending on the city centre alone at weekends, it can be seen as an "ideal target" for criminals.
However, high visibility police patrols in the city centre are sending a message to potential criminals, while also providing reassurance for the public.
Chief Inspector Alan Porte - the officer in charge of policing the city centre - urged the public to be vigilant.
Mr Porte said: "When out and about, it is vital owners take care of their property.
"Following simple safety precautions, including keeping your bag close by, and preferably to your front, can help prevent theft.
"Keep personal belongings, such as purses, wallets, and mobile phones out of sight. Never leave your valuables unattended. There are criminals out there who will take advantage of vulnerable people, please be vigilant."
Police have stepped up patrols in the city centre's streets, in a bid to prevent crime.
Both uniform and plain clothed officers have been deployed and special action plans will be run, specifically to target theft and disorder.
Last month, the Evening Times revealed how gangs of thieves stole more than £140,000 worth of hi-tech mobile phones during a crime spree.
Thieves have targeted customers at busy pubs, clubs and restaurants in the city centre, since October this year.
More than 280 mobile phones, including iPhones, BlackBerrys and other smartphones, were snatched during a spate of thefts.Police revealed 58% of these incidents took place within licensed premises.
Opportunist thieves are targeting shoppers in the city centre, as well as people waiting in shop, bus and taxi queues.
Mr Porte added: "The phones which are being lifted on the street are either bag dips or distraction thefts.
"However, in premises, the thief is known to put a newspaper over a table and then remove the phone with the paper - basically slight of hand."
Thieves operate in groups or pairs and use diversionary tactics, such as trying to engage people in conversation, while the other thief grabbed their purse or wallet.
The gangs typically send one person into a pub or club to steal, while the others hang back outside.