The site was throwing 500 error. I can see frmtmp.php files being generated in all the wordpress core folders. The files keep on coming back when I delete them.
First of all don't panic. And follow these steps: http://codex.wordpress.org/FAQ_My_site_was_hacked
If you have backup use it for restore it. But this will not solve your problem because there are great change to be hacked again (for the very same reason you have been hacked this time).
Also try to remove wordress installation files to another folder in order to prevent hackers from reaching the hacking scripts.