Rather bizarre CCTV footage has emerged from China of a young man on a bus taking off an elderly passenger's shoe to smell and lick it.

In the footage, captured on a bus security camera in Shandong Province on Tuesday, the man can be seen smelling the inside of the shoe and licking the sole before giving it back to the shocked senior.

According to local media, it remains a mystery as to who the man was or why he behaved in such a way.