Yoon Seok-youl, the leading opposition presidential candidate, has increasingly faced questions about superstitious or unscientific beliefs, this time over his alleged ties to an anal acupuncture specialist that he claims to have no knowledge of.

The allegation surfaced Tuesday during the sixth TV debate among presidential contenders of the main opposition People Power Party, when one of Yoon's competitors, former Rep. Yoo Seong-min, asked him if he has met someone "known to perform acupuncture on a strange and particular area."

Yoon replied he had not.

The subject was likely a sore point for Yoon because only days earlier he had come under intense criticism for displaying the Chinese character for "king" on his palm, showing what his opponents described as an utter disregard for the democratic system and a reliance on superstition.

The latest fodder appeared in footage from an event in June, in which the self-professed acupuncture specialist is seen walking next to Yoon.

Yoo's campaign reprised the attack on Wednesday, issuing a statement asking "what is Yoon trying to hide by lying" about his relationship with the man.

Yoon's campaign fired back: "Not only did (Yoo) turn the TV debate into a quiz show on psychics, he is now spreading lies. This attempt to damage Yoon is nothing short of shameful."

On the video, a spokesperson for Yoon said the man had tried to approach the candidate at the event but was restrained by Yoon's aides.

Moreover, the man in question was a regular feature not only at political events attended by Yoo, the former lawmaker, but also other political heavyweights such as the ruling Democratic Party's presidential contender, Lee Nak-yon, minor People's Party leader Ahn Cheol-soo and former U.N. Secretary-General Ban Ki-moon, according to Yoon's campaign.

In between the back-and-forth statements from the rival campaigns, rumors also swirled of an alleged altercation between Yoon and Yoo following Tuesday's debate.

According to the former lawmaker's campaign, Yoon shook his finger at Yoo and threatened him with libel charges.

In fact, it was Yoo was who pushed away Yoon's hand and left when he offered a handshake, the latter's campaign claimed.

South Korea's presidential election is scheduled for March next year.(Yonhap)