French prosecutors are investigating a senior presidential aide who attacked protesters in Paris while wearing a police visor.

Alexandre Benalla, an assistant to President Emmanuel Macron's chief of staff, was filmed targeting a woman and a man during May Day protests.

He was caught on video by a student activist and left the scene once challenged on camera.

He was identified from the video by French newspaper Le Monde.

On Thursday, it emerged he was accompanied on the day by a reserve policeman and employee of Mr Macron's political party, Vincent Crase.

France's Interior Minister Gerard Collomb said he had ordered an investigation by the country's national police inspectorate.

"These two people had no legal right to intervene," he said.

What happened?

The incident took place in a popular tourist spot at Place de la Contrescarpe in the fifth district of Paris, where about 100 people had gathered on 1 May.

The original video, posted on social media by 21-year-old Taha Bouhafs, shows a man in a police helmet who is not in uniform joining CRS riot police after clashes erupted.

He grabs a woman by the neck, charging her down the street, before both disappear off-camera.

Shortly afterwards he returns to the scene, attacking another protester who had been carried a short distance by police before being left alone on the ground.

The man in the helmet, since identified as Mr Benalla, can be seen grabbing the young protester around the neck, hitting him in the head and apparently stamping on his stomach when he falls to the ground.

Mr Crase is also seen in the fray, holding on to the same protester on the ground before Mr Benalla grabs him.

Riot police do not appear to intervene. (BBC)