2001-2002 I live in France for a year. 8 months in Nantes and 4 in Paris.
During that time I was attacked 3 times by North Africans (Morrocans, Algerians and Tunesians) and swindled and threatened twice.
To begin with the threats, both incidents involved being in 2 separate call shops where I needed to go to make some phone calls. Both times involved the North Africans working there charging me far, far, far more for my calls than was the case. Calls that were only 3 or 4 Euros worth they claimed were 50 euros or more and when I told them it was impossible they threatened me and told me they would bring in some 'muscle' if I didn't pay the supposed money I owed them. The first time it happened, I thought it was a fluke, the second time I recognised a pattern.
As for the direct violence, the first time Some friends of mine and I were heading back home from the pub and all of a sudden a beer bottle nearly hits one of my friends, so there they were a bunch of North Africans in a car having fun at our expense, they chased us round the streets throwing bottles at us, one of my friends got hit in the head and received a minor injury. They backed off when the police appeared to be coming.
Second time I was walking home from a friend's place and group of them (6) surrounded me and accosted me. They pinned me to a wall stole my wallet and got some blows in at me, turns out later I had a mild concussion.
Third time I was leaving the gare de l'est and there were these North Africans 'selling books'. One of them came over directly to me and almost dragged me over to the stand, insisting I look at the stuff there and buy something. I refused and left. Turns out, he sent 2 guys to follow me as I was leaving, as I ducked into a store, hoping they would be gone, they suprised be later in small street and pulled knives on me. Luckily just as something was going to happen a large group of people were heading our way, so I took this as a cue to run like I never ran before and got the hell out of there.
That happened to me.
A friend of mine living in Brussels at the time had his flat broken into by North Africans, who tied him up and beat him to a pulp, stole numerous thing and openly made threats (probably just to scare him) about murdering him. He had to be hospitalised for weeks afterwards.
More recently another friend of mine in Germany was sharing a flat with a bunch of people, 2 of which were North Africans who apparently hadn't paid rent for over 3 months despite my friend being very polite about it. When they were confronted about it one of them threw a bottle at him and threatened him with violence. Eventually the police had to get involved. Needless to say, it was a big mess.
They used to be almost only in France, now they are everywhere. Very sad.