10 Blank annonymous comments on all 2000 posts cant remove looks like bug

I am using the latest version of wordpress, recently I found that, there are blank anonymous comments on my site with no content no email and no name, i can’t edit or remove them because they don’t have any id attached to them. They donot appear in the comment moderation list.
There are about 10 comments in each post, i think its a bug.
Site link is exambazar.com