The 14-year-old boy from Putney had been talking on his Nokia mobile phone while waiting at the Cromwell Road bus garage, at 4.30pm on May 5.
He was approached by a gang of five teenagers who demanded he hand the phone over.
When he refused the men forcibly searched him and stole the phone.
Two men were arrested and were released on police bail. Police are still looking for witnesses.
Telephone PC Andrew Simpson on 020 8247 4946.
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