US rapper knocked out mid-performance after stranger charges on stage

US rapper XXXTentacion has been filmed collapsing after an unidentified man raced across the stage and punched him in the head during a concert.

The 19-year-old, born Jahseh Dwayne Onfroy, was performing in San Diego last night when he was coward punched while singing, TMZ reports.

Numerous videos of the attack, taken by attendees and posted on Twitter, show XXXTentacion being struck and falling unconscious on the stage.

Security immediately pounces on the attacker, knocking him to the ground and punching him repeatedly while scores of attendees and what appear to be venue staff swarm the stage.

Fights break out between different parties, while one person tends to the injured rapper.

XXXTentacion’s vocals can be heard continuing while he lay unconscious on the stage, suggesting he may have been lip syncing the concert.

He has since posted a video online condemning the venue and has threatened to sue.

No one as of yet has been arrested in relation to the assault, TMZ reports.