Validate max number of multiple files that can be attached in Laravel Validation

I have a form that allows multiple files to be attached.

I am validating the form for attachment field as:

$this->validate($request, [

            'attachments.*' => 'mimes:jpg,jpeg,bmp,png|max:5000',
        ]);

It works properly but I also want to only allow maximum of 3 files to be uploaded at a time.

How do I achieve this ?

via Chebli Mohamed