ATAC opens investigation into "very serious" incident.

A video that appears to show the driver of a Rome city bus deliberately knock down a pedestrian has been published online by Micaela Quintavalle, a well-known trade unionist and former employee of ATAC, the capital's public transport company.

The incident appears to have taken place following an altercation between the pedestrian and the driver of the bus, reported by Quintavalle as the number 786.

ATAC says it is treating the incident "very seriously" and that - once identified - the driver will be suspended.

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