to report neighbours' dog's aggressive behaviour

[abitshaken]

New neighbours got a very large breed dog - some mastiff mix, I think. Definitely well over 100 pounds in weight.
The dog is openly aggressive to people on the street (growling / snarling, lunging etc), and the owner is barely able to restrain the dog (actually, she just digs her heels in to slow the dog down, but is still dragged along). The dog is being walked late at night, but I already had an encounter with them, as did my friend who was leaving my house late-ish.
AIBU to report this even though the has been no injury / actual physical attack yet (to the best of my knowledge)? I just feel very unsafe in my own neighbourhood now.
If I report it, will there be any action taken?

Not sure that the authorities would do anything but I think they should. People who own untrained dogs, or indeed, train the dog to be violent and attack should be locked up.
Can you report it on the grounds of ‘threatened violence”?

Unless the dog actually hurts someone or is being neglected then no one will really take action, that's the experience I've had anyway. It's awful and I've had 5 years straight of it in 2 different houses. All day every day barking and aggressive behaviour whenever I stepped outside. My council might just be rubbish so I hope you get somewhere if you do complain!

I would report it. That dog could really hurt or even kill somebody. I don't know if the authorities will do anything about it but that will be their decision and it won't be your fault if they don't. I would be really worried if a dog that size and strength and of that breed was living near my family and showing aggressive behaviour. It could manage to escape its owner's grip one day and then what?

It's terrifying isn't it! My neighbours don't respect me and just let their giant Alsatian roam in our shared gardens/access to the front doors. It always barks and lunges at me aggressively, even after 2 years of living here! It's clearly trained to be like that. It's tried to get in my house several times when my 2 year old daughter has been stood next to me. I should be able to open my door without someone's dog trying to burst in and possibly attack us as it doesn't know any better! It just thinks I'm on its territory. It's got to the point where I just use the back door now. I wish there were more regulations on who can own powerful dogs, I've met some massive softies but there's a select few that would chew your arm off given half the chance!

Why the hell would anyone want a dog like that in their house unless they were drug dealers. Weirdos.

Thank you for thoughts. I reported it to the local police via online form.
That dog could really hurt or even kill somebody.
That is what terrifies me. I am a relatively experienced dog owner (medium sized breeds though), and I could see this dog goes into a full attack mode, completely unprovoked. I actually have not seen behaviour like this in dogs before at all. I don't think the owner takes it seriously as the dog was not even muzzled (although she was clearly very familiar with its behaviour).