$php app/console assetic:dump
Then run :
$php app/console assets:install --symlink web
to install the generated files from previous step.
After installed, we can use asset_url in twig as usual.
The problem occur when jquery-ui css file trying to find images in the url.
The solution is to move the whole jquery-ui images directory :
to Symfony 2 web css dir. So the directory will be like :
And your jquery-ui css will run as it supposed to be. (: