WordPress Admin Dashboard redirect to 404 Error

Hi,

I am having this error where whenever I try to access admin dashboard it takes me to 404 page of wordpress blog.

And at the top addressbar I get URL like this :

example.com/wp-login.php?redirect_to=http%3A%2F%2Fexample.com%2Fwp-admin%2F&reauth=1

404 error however uses wordpress page though with this message:

You are here: Home / Not found:
Not found, error 404

And rest of the blog is functional, no downtime of any sort. All the pages are accessible etc.

Is this issue from WordPress rediction or is it error due to host?

I tried to rename plugins and logged into the dashboard, it does give me access to login but if I rename the plugin folder back then redirection loop begins again. And sometimes even after renaming the plugin folder does not give access to the dashboard login either.

So what could be the problem?