Balaclava-clad youths reportedly chased four children near the McDonald's branch in Longwell Green.
The attempted robbery happened at about 2.30pm on Saturday, January 18 in Aspects Leisure Park, Leisure Road, police say.
A woman posted to the Kingswood People Facebook group: "My son was just cycling from McDonald's to Asda through the lane with his friends and they got approached by a gang wearing masks and balaclavas trying to get their bikes off them.
"Luckily they said no and got away quick. Please be cautious."
An Avon and Somerset police spokesman said a 14-year-old boy and three friends were riding their bikes on the footbridge near McDonald's when they were approached.
He added: "It involved a group of youths, some of whom had their faces covered, who asked for a ride on their pushbikes.
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"The four cyclists declined and rode off, pursued by the group.
"The incident has been filed, pending further information being made available. Anyone with information on the incident is asked to contact us, quoting reference 5220013886."
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