sort array of strings with čšž


I have problems with sorting array of strings with special characters (č
š ž),

%w"abcčdesšuvzž".sort => "abcdesuvzčšž"

the right order should be č after c, š after s and ž after z.

I write my own sort method:

sort_order = ['a','b','c','č','d','e','f','g','h','i','j','k','l',
user_items.sort_by {|u| sort_order.index(}

But it only works, if im sorting by first character.

How can i sort the whole words with right order?

example: %w"audi, bmw 320i, ,bmw 320d, seat, škoda, ...".