Police are urging clubbers to keep their mobile phones safe and secure when they are out and about in Leicester.
Senior officers believe travelling gangs of professional thieves may target the city's bars and nightclubs in the next few weeks.
Past experience has shown that November is a peak time for sneak thefts of phones at night-spots.
Officers the thieves target towns and cities such as Leicester after spending the summer stealing at music festivals.
City centre police commander Inspector Simon Preston said officers have been speaking to licensees, door staff and bar workers to encourage them to look out for suspicious characters and to warn their customers to keep their possessions safe.
They are also spreading the message among the city's student population.
In a typical month, city centre police record approximately 50 personal thefts, chiefly of phones.
Last November the figure rose to 126. Officers blame out-of-town thieves for much of the sharp rise.
Insp Preston said: "There are organised groups out there who come here with the sole intention of stealing phones.
"We had a significant rise in thefts last November and we are now looking at what we can do to prevent it happening again.
"The patterns is that we have a lot fewer thefts in the summer.
"There is a theory that organised criminal gangs go to festivals in that period."
Police urged people heading for the city centre to keep their phones secure at all times, ideally in a zipped-up bag or inside pocket.
One bar manager, who asked not to be named, said: "Our staff are trained to give people a gentle reminder to keep their stuff safe, particularly phones and bags.
"Our door staff are really good at spotting people who they think are going to get up to no good."
Jane Harding, 22, a student from Aylestone, said: "People need their phones with them when they're having a night out because they want to take pictures, send texts and just stay in touch with their friends.
"But you see loads of people leaving them lying around on bars on their tables.
"One of my friends has lost at least two phones like this in the past couple of years, so we're always on at her to keep it safe in her bag or in a pocket."
