How to compose a regular expression in location nginx?

Question

Nginx

There is a url like this:
/{locale}/seo/text.txt
For example:
site.com/en/seo/text.txt
site.com/ru/seo/text.txt
site.com/fr/seo/text.txt
...
I need to intercept location and change the root path, like this:

location /ru/seo {
        alias /client/www/public/seo;
}

This option works, but I need to do it with all languages, that is, something like this:

location ~ \/([a-z]{2})/seo$ {
        alias /client/www/public/seo;
    }

The problem is that it's impossible to start a regular expression in location. Tell me, please, how can this be done?