R&B star Monica and rocker Pete Wentz have reached out to rapper Kid Cudi to offer their support as he battles severe depression in rehab.

The Pursuit of Happiness hitmaker took to Facebook on Tuesday night (04Oct16) and revealed he had checked into an undisclosed treatment facility, admitting he hasn't been "at peace" for some time and had been secretly struggling with serious anxiety and suicidal tendencies.

Fans flooded his social media pages with messages of support and encouragement, and among those keeping Cudi in their thoughts were The Boy Is Mine singer Monica, whose ex-boyfriend committed suicide in front of her back in 2000.

Alongside an Instagram photo of Cudi onstage, she wrote, "Sending lots of love, prayers and support to @kidcudi... I don't know you but I know that God is able.

"I have not experienced this journey from where you sit but I watched someone battle depression & they're no longer here to tell the story... I claim in the name that it will be different for you & you will help others once you conquer all that you're faced with."

Monica went on to praise the rapper for going public with his personal struggles, adding, "What you shared took great courage & I pray you get enormous positive vibes & sincere support... Blessings to you."

Fall Out Boy bassist Wentz also applauded his pal Cudi for his honesty, as anxiety was an issue he struggled with as he battled prescription drug addiction in 2009.

"@KidCudi speaking out and letting the world see your humanity is inspiring - always got your back my dude...," Wentz wrote on Twitter.

Meanwhile, rapper Theophilus London tweeted: "Sending my love to @KidCudi we love u legend", and singer/actress Victoria Justice posted, "Wishing you the best @KidCudi... sending love & positivity your way."