A BBC Radio 1Xtra live gig in Birmingham was abandoned mid-event on Saturday night after the rapper Krept was slashed backstage.

West Midlands police said a man, whom they did not name, had sustained a slash wound at 10pm during an assault in the backstage area of Arena Birmingham. He was treated by on-site medical staff and did not require hospital treatment.

The wounded man was 29-year-old Casyo Johnson, one half of the UK rap duo Krept and Konan. In the early hours of Sunday morning, Konan (Karl Wilson) tweeted in reference to Krept’s condition: “Bro’s good.”

Later, responding to concerns, Krept himself tweeted: “My people thanks for the messages Im good, ill be back in no time. God was with me trust me. Cant keep a good man down.”

He later added on Instagram: “Was really looking forward to this week so I’m keeping the same energy I had, it’s gonna be a good week. Thank you for all the messages I’m good truss me. Could have been a lot worse. Stay positive my people. Happy Sunday.”

The sold-out show at the 15,800-capacity arena was being livestreamed on 1Xtra, Radio 1 and BBC iPlayer.

The event, advertised as starting at 7.30pm and finishing at 11pm, was due to include performances from the likes of Aitch, French Montana, Ms Banks and headliner Wizkid. Krept and Konan were not among the listed performers. Fans said the gig was halted without explanation, other than an apology, shortly after a surprise performance from the garage star AJ Tracey, prompting boos from the audience.

A Radio 1 spokesman said: “Following an isolated serious incident, we have had to stop 1Xtra Live in Birmingham. We are cooperating fully with the police to establish what has happened.

“We’re sorry to everyone who attended 1Xtra Live in Birmingham for the early finish. However, the health and safety of everyone involved is always our top priority.”

DJ Semtex was among those expressing hopes of a quick recovery for Krept. The hip-hop DJ also questioned why someone would “hurt one of the most positive and progressive artists out here? He’s been selflessly putting people on, investing in his community, giving back to the culture, and helped build the scene into what it is today.”

The MC Lady Leshurr tweeted: “Wtf all this madness on twitter I’m seeing Prayers for Krept.”

In 2015, Krept and Konan won best hip-hop act and best album at the Mobo awards. On the back of their chart success they have opened their own after-school programme – Positive Direction – and restaurant, Crepes & Cones, in Croydon, aimed at helping people from their local community.

Police said no arrests had been made in connection with the incident but officers were speaking to potential witnesses and reviewing CCTV footage. They asked for anyone with information about the assault to get in touch.

There was an unrelated arrest of a 23-year-old man on suspicion of possessing a knife at the Arena Birmingham on Saturday night, police said.