Incorrect url in compiled css file

I am using laravel mix to compile the sass files in laravel.

My webpack.mix.js file contains:

mix.js('resources/assets/admin/js/app.js', 'public/js/admin.js')
    .sass('resources/assets/admin/sass/app.scss', 'public/css/admin.css');

When I compile the files I get css files with wrong path to the fonts and images. e.g.:

url(/fonts/vendor/bootstrap-sass/bootstrap/glyphicons-halflings-regular.eot)

whereas the url should start with '../fonts' because the compiled files are under following folder:

• public/css
• public/fonts