I do believe that barn owls are common all around the world. The murderous sounds could easily be made by barn owls. When I first heard them, I believed it to be a child screaming. The time of day sounds right, and owls, as with all birds, would have more than one "voice" If you visit: www.allaboutbirds.org you can find a sound track of a barn owl. This may help in your identification. You are also likely to have a similar site for European birds, try Birds International perhaps.

It sounds like a Magpie. The get louder and more aggressive sounding when they are warning off another animal- predator getting to close to their young. They will land right next to my cat and chew him out the birds have no fear, I swear. Obnoxious birds that do horrible things to other bird's eggs and young. They stick around if there is a good food supply.

What that sounds like to me is the leptoptilos crumeniferus, and the only thing I can recommend to you is that you get the hell out of that house

This was the third night when I woke up to a strange bird sound. At first it is like a screaming-whining ( this is when I think I'm about to get brutally murdered) and then it becomes a more "peaceful" calling. I suppose there are at least 2 of these birds since they often answer to each other. I also firmly believe that it must be an owl, since I always hear it around 1-3 am.

note: I live in Middle Europe, so it must be some kind of an European owl (if it's not something else)

note2: the sound you can hear in the video is the "peaceful" calling, I always try to record the loud "screaming" calling, but as soon as I grab my phone they start the more peaceful calling.

so here is the video: https://vimeo.com/101906748

thank you!