I had previously read reports of Eva Green nudity in 300: Rise of An Empire, but this review in Recapped.com's comment section is the first one with details.
"Have seen an early cut of 300: Rise Of An Empire, and there is an impressive – and angry – sex scene for Eva Green, with lots
of her quite fantastic boobs.However, despite her nudity in the first film, Lena Headey stays clothed this time."
"The Eva Green sex scene in 300: Rise of an Empire is five minutes long, after a stand-off/argument between her character and Sullivan Stapleton’s. The anger between them turns into sex. It looks like she is going to dodge nudity, as for the first half of the sex scene, she keeps her top on. However, it gets ripped off and her glorious boobs are unleashed. No butt, if I remember correctly. Possibly his, unfortunately. No full-frontal either."
http://www.recapped.com/celebrity-nudity-rumors-december-18#comment-123009
300: Rise of An Empire premieres in theaters on March 7, 2014.