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Now this means war!!!

Amanda Nunes says Ronda Rousey UNFOLLOWED her on Instagram -- and made it so Amanda can't see what's going on her social media page ... which means she was BLOCKED!!!

The UFC women's champ is in L.A. to promote her big fight at UFC 207 on Dec. 30th -- when we asked if she's seen the buffed-out pics Ronda's been posting on Instagram lately.

That's when Nunes told us Ronda unfollowed her recently -- and explained that in addition to that ... she can't see anything on Ronda's page!

BLOCKED!!!

But is Amanda bothered by the cyber diss? Hell no.