CHICAGO (CBS) – Police patrols will be stepped up this weekend in light of the recent wilding and “flash mob” attacks in downtown Chicago, CBS 2 has learned.

North Avenue Beach.  Oak Street Beach.  State and Chicago.  Navy Pier.  Sources say these locations will have beefed-up police presence this weekend as the temperature rises.  Sources say the move comes after an increase in disturbances.

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In one incident last month at North Avenue Beach, sources say a group of about 100 teens surrounded two people on bikes.  Both were knocked off their bikes and thrown into Lake Michigan.

Bicyclists say the increase in security is welcome.

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“Yes, it makes a big difference,” bicyclist Olavi Goos said.

It’s not the first time police have responded this way. Last year, activity by flash mobs was also met with heightened police presence. Officers increased foot and bike patrols and searched bags at different lakefront locations.

Sources say once the plan was put in place then, the problems stopped.

Ever since the recent flash mob and wilding incidents have been reported, police patrols have been stepped up in the city, including at State and Chicago.  The spot is known for criminal flash-mob activity.  Teens post messages on Twitter or Facebook about meeting there, then carry out their plans. 

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Sources tell CBS 2 News in the past month, there have been more than 35 arrests for flash mob and wilding incidents in the city.