In France's second city, deep-rooted frustrations have bubbled over into looting and vandalism.

Kaouther Ben Mohamed fights for better rights for the poor. She says the destruction here is sad but it's not surprising given the frustration many residents feel.

"There's a double discrimination in Marseille compared to the rest of France," she says.

"The first is the colour of your skin and your surname. The second is where you live. For people who are called Sofiane or Mohammed, it's more difficult living in a working-class area, having access to schools, accommodation and getting a job."

Poverty, racism and drugs mean clashes with police aren't rare here, but this widespread looting is an escalation and a worrying sign.

The damage is a step-up because the violence has penetrated the heart of the city rather than being contained in the poor estates on the edges and that speaks to the level of anger people are feeling.

"Nahel's death was the final straw for people in the working-class areas and for young people because there are so many other Nahels, there's so much other police violence," Kaouther explains.

And so, this week, the crowds returned to the streets, undeterred by the tear gas and rubber bullets.

We watched as some defiantly taunted the police, holding glowing flares aloft.

On the sidelines, we saw young people lighting fires, burning whatever they could find or ripping up road signs as makeshift weapons.

While many seemed motivated just to make trouble, others had come with a message like Hamza, who says: "The police in France is racist."

He says the violence is a backlash following years of police racism and discrimination.

"There's lots of looting here in France, because what do they [the police] do? They shoot at us and people loot for revenge," he told me.

"When you live in a district in France, they hit you. It's the same all the time... They hit you, they rob everything you have and then they throw you out. It's all the same if you're Arab, black, or Chinese. It's always the same," he said.

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On Friday, the UN rights office called on France to address racism in the police.

"This is a moment for the country to seriously address the deep issues of racism and discrimination in law enforcement," spokesperson Ravina Shamdasani said.

France rejected the accusation.

Just after we spoke to Hamza, we watched as police dragged a protestor roughly to the floor and arrested him in front of a furious crowd.

Scenes like this won't help build trust but neither will a video which emerged reportedly showing rioters looting about 20 cars.

The shooting of a teenager sparked the unrest in Marseille.

Now, long held divisions continue to fuel it.