Url routes to greek

I am trying to set in my Url-Uri Greek chars (for SEO purposes). 
I am a new member and I started to learn for version 2.2.6. 

So far this works: 

$apartment = urlencode('διαμερίσματα');
$wild = '/(:num)';
$wildsecond = '/(:any)';
....
$route[$apartment] = 'page/apartments'; //works
$route[$apartment.$wild.$wildsecond] = 'page/apartment/$1/$2'; // not working

Also I tried to change config file to this:

$config['permitted_uri_chars'] = 'a-z 0-9~%.:_\-'.
   'αάβγδεέξηήθιίϊκλμνξοόπρσςτυύϋφχψωώ'.
   'ΑΆΒΓΔΕΈΖΗΉΘΙΊΪΚΛΜΝΞΟΌΠΡΣΤΥΎΫΦΧΨΩΏ';

But it didn't work so far for the route of wildcards. 
WHAT can I do?

Maybe a typo?

'page/apartment/$1/$2' missing s in apartements

No it isn't a typo. It works only for English letters... not for Greek ...