In my apartment complex (high rise) the management staff often enters unit without prior notice. They will just knock twice and enter the unit without giving you enough time to reach the door and open it for them. If you are not in the apartment then you won't even know who had entered and what they had done in your apartment. At least 3 times they have entered while I was inside, no time for me to get to the door as they were already in. All maintenance guys carry the keys to the apartment units.
I have rented apartments in US and have never had this type of thing happened there even though the management was really bad.
I just googled about the apartment and have come across 2 posts/reviews of the apartment with similar complaint of entering unit without notice. I'm going to write a lengthy review of apartment which will show up for anyone that google's for its name/address.
For anonymity reasons I don't want to name the apartment in this thread.
Does this happen in your apartment complex's too?