Drafts cannot be deleted all at once

i have wp-o-matic, and i fetch several feeds. i take the fetched feeds to the DRAFTS page and choose what to publish. Now, my DRAFTS are just too many (200+) and so i tried deleting them all at once. No luck. It always returns me a WordPress error message. Is there any solution to delete drafts at once rather than deleting them one by one, which is tasking..TIA..