Biden said some of what he has seen at McCain events is 'scary stuff.'

(CNN) — Joe Biden said Monday some of the reactions he has seen at recent McCain campaign rallies are downright “scary,” and said the Republican presidential ticket should be careful not to encourage "fringe people."

But in the interview with ABC News, Biden added he does not worry the McCain-Palin rallies could lead to violence as long as John McCain and Sarah Palin adequately control their supporters.

"I'm no more concerned about it, as long as … John pushes it back in a box and Governor Palin pushes it back in a box, because what you don't want to do is encourage — I don't think they intentionally do it — encourage people who really are fringe people," Biden said in the interview. He also said that what he saw at the rallies was "really off the wall" and "scary stuff."

Earlier: Biden: McCain’s speech is ‘attack, attack, attack, attack’

Biden also took aim at recent comments from Virginia’s Republican Party chairman that compared Obama to 9/11 mastermind Osama Bin Laden. The chairman, Jeffrey Frederick said Obama and bin Laden "both have friends that bombed the Pentagon" — a reference to Obama's connection to 1960's radical Bill Ayers.

"I don't believe it … I can't believe it," Biden said of those comments. "I'm surprised John McCain hasn't gone down and whacked the guy with his fist. I mean, I don't think there's a prejudiced bone in John McCain's body. But that kind of stuff is really off the wall. I refuse to let myself believe John McCain has anything to do with any of that.”