You can try orange and lemon peels (cats dislike citrus scents), the herb rue which can also be planted live, cayenne pepper, coffee grounds, pipe tobacco and various oils, including lavender, lemon grass, citronella, peppermint, eucalyptus and mustard.
Talk with the neighbours if this fails;
If politely talking with your neighbor fails to solve the problem or feral cats are being a nui- sance, contact your local animal control office and ask for their advice and assistance. If the animal control office is not helpful, contact your local elected city or county officials and ask for their help.

Borrow a friends dog for a few days an hopefully the cats will think a dog lives there and not return.

We also hear the cats 2 doors over and it is very loud,thought it maybe possums fighting with the cats also!

There could be a female cat in the area on heat and the males want to get to her and are fighting for that right,,, I have found the cats in our area only do it for short periods of time.. But seriously if you know who the owners are i would have a friendly word to them as they shouldnt be straying from their households at night.. and if its the male cats that are dong this they might need to get the snip if they havent had it… Although i do have to admit i love the neighbours cat visiting our yard as its keeping the mice away… But it doesnt go fighting with other cats…

I would recommend to spray citronella around your garden it is a natural deterrent cats hate the smell, i think squirting with the hose would also work if you can actually catch the little buggers. The other thing i would recommend is talking to your neighbours about it and asking if they can keep their cats in between the hours of dusk and dawn in most councils now you have to by law otherwise call your council about the issue to see if they can help in anyway with traps or catching themselves. Good luck

I would be getting out there on the garden hose, giving them a blast with cold water. Not very friendly but drastic measures call for drastic actions

I’d squirt them with the hose

I would talk to the neighbours as first thing. Maybe they understand the situation and they try to keep them inside at night. Otherwise I think I would try with the hose too. Difficult!

If they are also using your garden as a toilet put lemon or orange peel in your garden beds as they don’t like the semll of it. Put the opening upwards. Are the cats desexed?? Sometimes cats are defending their territory.
By law (I don’t know if it is Australia wide) cats have to be locked up at night. If you don’t want allow them the run of the house shut them in one room such as the laundry, a fully enclosed carport or a shed. They need water and if you don’t want a “mess” a litter tray. You should explain to your neighbours the problems you are having. If they argue about it explain that is the law. I don’t know if it applies to all states but in some you also need to have your cat microchipped or tattooed (not sure which). There was also talk of registration of cats in Vic. a few years ago.

In the good old days we used separate both dogs or cats with water from the hose. It’s something they don’t like and it usually deters them for quite a while.