Nginx Serving Blank Page for Wordpress

For a wordpress site hosted by nginx 1.6.2 running on Ubuntu 14.04, the server suddenly starts serving a blank page when accessing it at www.mysite.com. Wordpress files are located at /var/www/wordpress. It used to work, but after an update it stopped working and shows blank page instead.

nginx logs at /var/log do not show anything. The page title shows 403 Forbidden

Any suggestions? Below is my config file:

server {
    listen 80;

    root /var/www/wordpress;
    index index.php index.html index.htm;

    server_name mysite.com www.mysite.com;

    location / {
        try_files $uri $uri/ /index.php?$args;

    }

    error_page 404 /404.html;
    error_page 500 502 503 504 /50x.html;
    location = /50x.html {
        root /usr/share/nginx/html;
    }

    location ~ \.php$ {
        fastcgi_split_path_info ^(.+\.php)(/.+)$;
        # NOTE: You should have "cgi.fix_pathinfo = 0;" in php.ini


        # With php5-fpm:
        fastcgi_pass unix:/var/run/php5-fpm.sock;
        fastcgi_index index.php;
        include fastcgi_params;
    }

}

In php5-fpm's www.conf:

user = www-data
group = www-data

Setting file/directory permissions to 777 to the directories and files being serve do not help.