"(I) cannot confirm it," Song said during a parliamentary session in response to a question about whether he could clarify if Kim was involved in the deadly attack or not.

"We can make presumptions about the North Korean situation, but it is impossible to confirm anything," he added.

But the minister said he believes that the communist state is responsible for the sinking of the Cheonan.

"I understand that (the submarine that carried out the attack) was the North's Yeoneo-class midget submarine belonging to the RGB," he said.

Pyongyang is known to have an assortment of submarines, including 130-ton Yeoneo-class submarines, 300-ton Sangeo-class submarines and 1,800-ton Romeo-class submarines. 

Conservatives, along with the families of the deceased victims of the torpedo attack, have strongly protested Seoul's acceptance of Kim as a North Korean delegation chief. They have called Kim a "murderer" and "war criminal," and demanded President Moon Jae-in's apology.

Apparently mindful of the political offensive, Moon held a low-key, closed-door meeting with the North's delegation in the northeastern alpine city of PyeongChang hours before the closing ceremony of the Olympics on Sunday.

The liberal Moon administration has been gingerly striving to use the delegation's visit to maintain the growing momentum of inter-Korean rapprochement, though Washington, its key ally, appears to be at odds with its dovish approach, hammering away at its "maximum pressure" campaign. (Yonhap)