I have written a couple of articles for 2 different daily newspapers. In them, I have discussed the issues of my academic field. Should I include them in my CV?
Yes, certainly, as long as you clearly separate them from your academic publications. Strictly speaking, they are form of publication, so it wouldn't be lying to list them together with your research papers under a vague enough title, but this would be a very bad idea. It would come across like you are trying to make your publication list look longer by inflating it with non-academic publications.
[If the newspaper articles had nothing at all to do with your academic work, then mentioning them probably wouldn't make sense. However, it sounds like they do.]
If so, under what title? Is press release appropriate? What is the most common and accepted term?
Definitely not press release, since a press release is something else: it's a document given to journalists to inform them about a possible story they could write about. Occasionally newspapers publish lightly edited versions of press releases, without gathering much more information, but this is considered bad reporting.
I don't think there's a clear standard for how to list this information. You could list it in several ways: outreach, other publications (if you have a "scholarly publications" section, say), writing for the general public, etc.