The Twittersphere was alive Monday with discussion about an eye-popping performance by rapper Tupac Shakur at a US music festival -- 16 years after he died.

The vividly life-like hologram performance, which was in the top 10 trending topics on Twitter and mentioned at least 40 times a minute, shocked some fans at the Coachella music and arts festival in Indio, California.

Tupac, who was gunned down in 1996 in Las Vegas, appeared to rise from the stage, asking "What up, Coachella?" before being joined on stage by flesh-and-blood rap stars Snoop Dogg and Dr Dre.

As fans looked on in disbelief, the bare-topped star, with pants sagging and neckchain swinging, then joined Snoop Dogg on "Come With Me," "Hail Mary" and "Gangsta Party" at the performance Sunday.

"That hologram form of tupac look sooooo real!!!!!!! Technology is a beast!" commented @iamPink_Lipss, while @AyyOnline added: "This is insane!!"

A November 1994 attack on Shakur in New York triggered a rap war pitting West Coast rappers including Shakur against East Coast rivals represented by superstar rapper Notorious B.I.G, whose real name was Christopher Wallace.

Shakur was gunned down in Las Vegas in September 1996 and Wallace was shot dead in Los Angeles six months later. Both murders remain unsolved.

The annual Coachella festival is being held over two weekends in Indio, east of Los Angeles. As well as the from-beyond-the-grave rap show, the first weekend also saw British bands Radiohead and Kaiser Chiefs take the stage.

Not everyone on Twitter was excited about the hologram show. "Tupac is still dead you idiots," commented @maulingmueller, while @ChrisRRegan joked: "Right after it was unplugged, the Tupac hologram released another four albums."