Rapper known for Whoa! dies aged 51 in hospital after mystery illness. (Courtesy)

Rapper Black Rob has died aged 51.

The musician was best known for his 2000 instant hit single Whoa! and to many music fans on the hip hop scene.

He also featured on Diddy's famous track Bad Boy 4 Life.

Bad Boy Records rapper Mark Curry broke the news of the fellow musician's death on social media.

DJ Self revealed Black Rob had died in an Atlanta hospital.

It's believed Black Rob could have been battling with kidney failure, according TMZ.

Black Rob is dead. (Courtesy)

Tributes were flooding in for the late hip hop star on social media, with the pair leading the posts.

"Rob passed away about an hour ago."

DJ Self added: "Lord knows i tried to get help ...... I’m sad to say RIP to Black Rob ..... Passed away in the hospital in Atlanta....."

Otto Von Biz Markie wrote: "RIP Black Rob, one of the great millennium-era crime rap novelists, gruff but with Harlem slickness, who endured fire & brimstone to briefly reach the apex, before gravity and the law took hold.

"Of course, "Whoa," which owned the world for a full year, the platonic tunnel banger."

Previously, DJ Self had posted a video of Black Rob in a hospital bed paying his respects to the late rapper DMX.

DMX died after an alleged overdose triggered a heart attack.

At the time, the video of Black Rob had sparked concern for the rapper as fans wished him a speedy recovery.

Among the sea of comments, one fan wrote: "We can't lose 2 legends in 2 week."

Alongside the clip, DJ Self wrote: "Let keep our prayers up Black Rob !!! Get well man Please people out there take care of yourself BR was one of the greats Had NY on his back like Whaooo."

Black Rob had previously spoken about his battle with ill health including a number of strokes.