Spam issue in WordPress

Over the last 24 hours I have received 120 comments on the two post on the site. None of the comments were relevant, but instead offering me links to various “nice” pictures with young models…
I’m fairly new to WordPress but I do like the commenting feature, so that relevant people may comment on post. But I don’t like to go through all this spam to see if I miss a real comment on the sites.
Any one with a good suggestion a plug-in or something else to solve this matter in WordPress?
Login solution is not an option since this would require people to register up front and me to approve them etc. that would kill the idea of making it easy to comment on posts.