"Please understand that although it is no excuse, I was completely unaware that in Australia there is a polarizing social issue happening right now involving indigenous people and alcohol," he wrote.
"When I was made aware of it, the ground fell out beneath me, and I realized that people may now see me as the exact opposite of who I am. I'm sitting here in my hotel room completely gutted that a joke that I made was much more relevant to the times in Australia than I realized.
"I know that words are just words, but to those I offended, I deeply, DEEPLY apologize!
Everyone who knows me is aware that for the past 20 years I have been a fervent supporter of civil rights, so I am incredibly embarrassed by my ignorance.
"I feel like a fool and apologise to all Australians."
He then made another update, saying he "didn't know until TODAY that just the phrase 'black Australian' was racist all on it's own".
"I sat in my room and I cried when I found out," he said.
"In future it might be a good idea to learn a bit about the important histories of the countries you perform in before making such derogatory remarks re the Indigenous people," wrote one person who attended the show.
"I'm confused. How was your statement intended to be funny at all? I appreciate that you have found yourself in a situation where your words have deeper significance than you intended. And that you are sorry for causing that firestorm. But that still leaves the original joke linking excessive drinking with being a behaviour of our first peoples ... and I'm struggling to see how that could ever be appropriate or funny," wrote another.
Loyal fans were quick to post supportive messages in light of the singer's gushing apology, with one writing on Twitter: "Can we note that the comment made by Rob Thomas was made during lengthy technical difficulties and he was under a lot of pressure."
"At the time I thought 'woah! Not cool' but he stressed and just tried [sic] to keep talking. He has apologized- that's all we can ask," the fan added.
• This story first appeared on ZMonline.