The 14-year-old was dropped off in London Road at 8.30am on Monday 21 January, before walking up to the Cash Converters on Above Bar Street.
We have CCTV of her from 9.30am at the Cash Converters, but she has not been seen since.
Nadia is described as Asian, slim, 5ft 8ins tall, with long straight dark hair.
She was last seen wearing a white jacket, black leggings and blue trainers and was carrying a black shoulder bag.
Detective Inspector Steve Spencer said: “We are concerned for Nadia’s welfare as it has been three days since the last sighting of her in the city centre.
“It is out of character for her to go missing, and it is very cold this time of year so we want to ensure she is safe and well.
“We are appealing to Nadia to get in touch with us, or your family, so we know you’re ok.
“We also appeal to anyone who has seen her or heard from her since, or knows where she is, to get in touch”.
Anyone with information is asked to contact police on 101, quoting 44190025436.
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