Nginx rewrite rule (subdirectory to subdomain)

I would like to redirect admin subdirectory to a subdomain. I tried to create this rule for Nginx however it's not working:

location ^~ /admin/ {
        rewrite ^/admin(.*) http://admin.example.com$uri permanent;
     }

Thank you
Regards

Answer

Something like this should do the job:

location ^~ /admin/ {
    rewrite ^/admin/(.*) http://admin.example.com/$1 permanent;
}