Gwent Police said it was made aware of the video circulating on social media on Wednesday evening and that officers were supporting the young person as enquiries continue.
The force said in a statement that it was also aware of a “separate incident from earlier in the day, where a different child was reportedly assaulted”.
In a joint statement, the headteacher and chair of governors of the child’s school said they were aware of a “serious incident”.
They said it had taken place “after school” on Wednesday and involved “some of our learners”.
“Rest assured that it has been reported to the police and we will ensure a full investigation is carried out in cooperation with the police and the local authority,” they added.
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ACC Vicki Townsend from Gwent Police said the force “understood the worry and concern that incidents of this nature can cause” and thanked the local community for the information they had already shared.
“With that said, I’d also like to urge people to not speculate on social media but to contact us immediately if they have any details they think could help our investigation,” she added.
