The picture on the left shows a woman believed to be Kim Jong-chol’s wife, who went to an Eric Clapton concert with him in Singapore; the one on the right is his younger sister Yeo-jong as a child.

Speculation is mounting over the identity of a woman who was spotted with North Korean leader Kim Jong-il's second son Jong-chol at an Eric Clapton concert in Singapore on Monday.

She sat next to Jong-chol (30) during the concert, smiling and chatting with him, snapping photos and touching his arm in a way that suggests a close relationship.

Some believe the woman's chubby features suggest she is his younger sister Yeo-jong (24).

Yeo-jong is the daughter of Ko Yong-hui, who died in 2004, Kim Jong-il's third wife and also the mother of Jong-chol and Jong-un, the heir presumptive. But one South Korean intelligence official said the woman appeared to be Jong-chol's wife.

A North Korean source said Yeo-jong was chubby as a child, but not any more.