Two people were arrested after an influencer boxing event in Kilkenny, Ireland, descended into a riot late on Saturday night, with tensions in the crowd inflamed by the presence of the far-right activist Tommy Robinson.

The disorder began at about midnight at the Hub events venue, at an event organised by internet personalities Harrison Sullivan, known as HSTikkyTokky, and Ed Matthews under their Unhinged events company. The pair featured in a Netflix documentary about manosphere influencers earlier this year, and Sullivan had told the Guardian on Friday that Robinson would be attending. A chaotic press conference on Friday evening, at which competitors repeatedly attacked each other, foreshadowed the trouble to come.

Robinson, 43, whose real name is Stephen Yaxley-Lennon, was a ringside guest surrounded by supporters. He is on bail after being found guilty in October of harassing two journalists to the point that they feared violence, and is due back in court on 16 December for sentencing, with a substantial custodial sentence possible. The Ministry of Justice and the Metropolitan police were unable to confirm whether his bail terms prohibited international travel.

The event, livestreamed on the Kick platform to about 1.8 million viewers, began without incident. The atmosphere turned tense when Sullivan and Matthews invited Robinson to the commentator's desk before a fight involving the Muslim social media personality Mo Deen, whose real name is Mohammad Kubba. Robinson, holding a copy of his book The Grooming Gang Cover-Up, said that "Muslims have been raping our country for 100 years" and cited false statistics about Muslim men and sexual offences. Many in the racially diverse crowd took offence.

After Kubba won his fight, he climbed out of the ring and threw punches at Robinson before security brought the scuffle under control. The event then erupted when Sullivan demanded that Kubba, who had left the venue, return to "face off" against Robinson in the ring. A reluctant Kubba was escorted back by security, while Sullivan was repeatedly heard saying "let Tommy fight him" and allowed Robinson's entourage, whom he called "Tommy's boys", into the ring.

When Kubba entered the ring, now filled with Robinson's supporters, Robinson threw a copy of his book, which has Arabic-style lettering, at him, and a fight broke out. The crowd erupted into violence, with chairs and barricades thrown and attenders punching each other as others screamed and ran for safety.

Interviewed by the Guardian after the riot, Kubba claimed he had been told to start a fight with Robinson, though he declined to say by whom. Robinson had earlier said he would be willing to "batter" Kubba if the Muslim personality started a fight, while adding that he liked Kubba and bore no ill will towards him. There is no suggestion the riot was pre-planned.

Violent scenes unfolded over the next 20 minutes as Sullivan pleaded unsuccessfully for calm, before event security, venue staff and the gardaí, who had been called earlier in the night after disturbances, broke up the riot. A Garda Síochána spokesperson confirmed that a man in his 30s was assaulted and taken to St Luke's hospital in Kilkenny, a man in his 20s was arrested and detained, and a teenage boy was arrested and charged with violent disorder, with a court appearance due on Sunday.

Footage of the riot spread across social media in real time, and chants of "Oh Tommy Robinson" could be heard before the livestream cut to black. After police dispersed the crowds, Sullivan attempted to restart the fights for the stream only, but was blocked by a visibly upset representative of the venue.

In comments uploaded to social media on Sunday, Sullivan acknowledged he had erred by not hiring more security. "Everyone makes mistakes when you are trying to grow something," he said, adding: "One thing I can say is it was a great night of entertainment and it's gone super viral." Footage of the riot was also uploaded to the company's official Instagram account. Outside the venue in the early hours of Sunday, a crowd of mostly teenage boys and young men filmed the aftermath on their phones, with one attender telling the Guardian that such things did not happen in Kilkenny city, which has a population of 27,000.