The Norwegian defender slipped under no pressure and gifted Shakhtar their third goal in their 3-2 win over Roma.
“We played fairly well and I made an incredible mistake on the third goal, but I think we can win in Ukraine,” Riise told the Italian media.
“I know that the fans are against me now and I feel terrible about this. That is football, but this was truly a negative match for me.
“I was going to hit the ball long, but then I thought about it a moment more and lost my balance. I really don’t know how I did it. I’ve had a similar experience with an own goal in the semi-final for Liverpool. I feel just sick, even physically.
“I hope the supporters can understand that I always give my all. I apologise to them. I went off at half-time because I made a mistake.”