Oliver Conway

On the street below, rival drug gangs, heavily armed, often just teenagers, are fighting over turf.

We're going to kill you all, he says.

Night after night, some neighbourhoods in the ancient port city of Marseille are being transformed into war zones.

Footage of the dead circulating on social media.

Victims as young as 14, 15.

The cumulative effect of all these killings here in Marseille has created what people locally describe as a kind of psychose, a nervous panic, a terror that has gripped the city.

He's lifting up his vest here, T-shirt, to show me the scars.

He's got a big scar on his back.

Yusuf, a gang member, shows me where he was shot by rivals.

In the last few years, he says, the bosses are using young people, paying them next to nothing.

It's chaos.

I'm heading now to meet a local lawyer, somebody who's been active for years supporting the victims of gangland killings.

But in the last week or so, she's become so afraid for her own safety that she's taken a step back.

And she's going to talk to us now, but only if we hide her name.

We're seeing increasingly youngsters, teenagers involved in the gangs now.

In a big convoy, French police drive towards the outskirts of Marseille to an area where the drug gangs are dominant.

The aim is to disrupt their trade.

OK, we're just running with the French police here around an apartment block.

They're trying to seal off to make sure that there are no drug dealers here.

We're in a stairwell now.