The victim was walking in the Dandy Brook area when she was approached by the group between 3pm and 3.30pm on Tuesday, June 22.
The boys - two of which were wearing balaclavas - proceeded to kick the girl's dog before stealing her mobile phone, police said.
Officers believe the boys were around 16 years of age.
Police are asking anyone with information which may help them with their investigation to email [email protected], quoting log reference number LC-20210622-1207.
You can also call 101.
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