Bernie Sanders has said it was “beyond disgusting” that a man unfurled a Nazi swastika flag and shouted anti-Jewish slurs at the Democratic presidential candidate at his rally in Arizona on Thursday night.

Sanders, who would be the first Jewish US president if elected, said he was “shocked” by the incident at a rally in Phoenix. Many of Sanders’ relatives were killed in the Holocaust.

“I heard people booing but I didn’t realise [what happened] until I left the stage,” he said on Friday morning.

“I speak not only as a Jewish American but on behalf of the US troops who died fighting Nazism. It’s horrific, it’s beyond disgusting to see, in the United States of America, that people would show the emblem of Hitler and I was shocked to hear that later,” he said.

He pointed out that there is sometimes disruption at his campaign events “with Trump people”, but added: “This was something different” to “have someone bringing forth the most detestable symbol in modern history”.

He congratulated the Phoenix police for dealing with the incident and said he had not felt unsafe.

The man, who has been identified as a local far-right stunt activist who posts offensive material on YouTube, was quickly escorted out of the Sanders rally.

The man is reportedly very active online as a “stunt activist”, frequently posting videos of himself infiltrating events for Jewish and Muslim organizations on his eponymous YouTube channel. A spokesman for YouTube told the Guardian it had terminated the channel on Friday for violating the platform’s terms of service agreement, which bans content “promoting violence or hatred against individuals or groups”.

The Anti-Defamation League, an organisation that tracks antisemitism, recorded 1,879 acts of antisemitism in 2018, with a dramatic increase in physical assaults, including the deadliest attack on Jews in US history at synagogue in Pittsburgh, Pennsylvania.