Wordpress javascript and css fail to load after changing url

I wanted to add my blog, which is hosted in a different server, to my main website under subdirectory /blog.

The proxy through nginx went well

location /blog/ {
  proxy_pass http://107.170.8.156/;
}

I added also those lines to config.php

define( 'WP_SITEURL', '/blog' );
define( 'WP_HOME', '/blog' );

$_SERVER['REQUEST_URI'] = str_replace("/wp-admin/", "/blog/wp-admin/",  $_SERVER['REQUEST_URI']);

It works fine, however it fails to load css and js files

I searched everywhere on the Internet and I am not able to find any solution.

via Chebli Mohamed