US rapper Big Pokey has died after collapsing during a performance in Texas.

The artist, whose real name was Milton Powell, was performing at a Juneteenth-themed event at a bar on Saturday when he fell backwards on stage.

Witnesses rushed to help the 45-year-old before he was taken to a nearby hospital. He died on Sunday.

"He was well loved by his family, his friends, and his loyal fans," his publicist said in a statement.

"Big Pokey will forever be 'The Hardest Pit In The Litter!'", the statement added, a reference to the rapper's debut album.

Video circulating on social media showed Powell suddenly fall backwards with his microphone in hand while performing at the Pour09 Bar in Beaumont.

Paramedics were called shortly before midnight local time, a Beaumont Police spokeswoman told the Houston Chronicle. A cause of death has not been released.

Powell was best known as a founding member of the Screwed Up Click, an influential hip-hop collective of Houston-based artists.

It helped pioneer the city's "chopped-and-screwed" sound, a laid-back, low-slung, style produced by slowing the pitch and tempo of the underlying track.

Powell charted in the Billboard Hot 100 when he appeared on the Paul Wall single Sittin Sidewayz in 2005. And last year, he featured on Megan Thee Stallion's Southside Royalty Freestyle.

Various artists, including Juicy J, Slim Thug and Lil Flip, have paid tribute to Powell.

"Low key, humble mountain of a man who moved with honour and respect. He was easy to love and hard to hate," the rapper Bun B wrote on Instagram.