how to access controllers in 'admin' directory

[eluser]Blue Sapphire[/eluser]
I have created 'admin' folder in 'controllers' folder. I have created a controller (user) in 'admin' folder.

I have added following line in routes.php file :

$route['admin/(:any)'] = 'admin/([a-zA-Z0-9/_]+)';

I am using following url to access user controller in admin folder.

http://localhost/main/forum/admin/user/

My application is routed to default controller.

Can someone guide me what Iam doing wrong and how it can be rectified.

Thanks in advance