Ryan Phillippe has been hospitalised with a mysterious injury.

The 'Cruel Intentions' actor revealed on his Instagram account he'd been forced to seek medical treatment on his leg, but didn't go into detail and reassured his fans that he's on the mend.

The 42-year-old star posted a photo of his injured leg on his Instagram Story with the caption "not lit", and later shared an image of himself lying in his hospital bed giving a thumbs up.

He captioned the post: "i'm going to be ok & i appreciate your concern. -[heart] me (sic)"

Earlier in the day, Ryan had shared a photo of his hand covered in small plasters but it isn't clear if the injuries are connected, or if he'd sustained them working on his TV show 'Shooter'.

The actor recently admitted filming the drama, in which he plays an exiled marine, is very tough and pushes him to his limits.

He said: "It's a tough show to shoot. The last two weeks we've been in the desert, Palmdale, you know, in degrees over 110. And it's a physical show, and I do all of my own stunts.

"We kind of really push it to the limits. But I love it at the same time. It's exhausting. I've got bruises. But it's going really well, and I'm excited about people seeing this new season...When the season ends, I'm going to go on a bit of a break and heal."

Meanwhile, Ryan - who has 17-year-old daughter Ava and 13-year-old son Deacon with ex-wife Reese Witherspoon, as well as six-year-old daughter Kai with ex-girlfriend Alexis Knapp - recently admitted he loves spending his free time with his brood, doing anything that "gives [him] some relief" from his job.

He said: "Usually, a great day off involves doing something fun with my son. I think we are going to go off-roading this weekend. That is something we are getting into. Whatever takes me out of the job and gives me some relief."