SEOUL (AFP) - North Korea's next dynastic succession may have been secured, with new television images of leader Kim Jong Un's wife suggesting that Pyongyang's first lady recently gave birth.

When state tv showed Ms Ri Sol Ju attending a memorial service for her husband's late father Kim Jong Il in mid-December, she appeared heavily pregnant with her loose-fit traditional dress barely hiding a swollen belly.

But more recent images of her attending an official New Year's party showed her wearing a well-fitted two-piece skirt suit with no physical sign of pregnancy.

Speculation was fuelled by the official performance, which included an all-woman band singing a version of the Christmas favourite "When a Child is Born" made popular by Johnny Mathis.

South Korean television and newspapers on Thursday ran before-and-after photos with speculative captions.

"The bulging stomach has gone down ... has Ri Sol Ju given birth?" asked the Dong-A Ilbo daily.

"Ri Sol Ju with her tummy reduced in 11 days. Has she come out right after childbirth?" ran the caption in the Chosun Ilbo daily.

A South Korean government official, quoted by Yonhap news agency, said Ms Ri "appeared to have already given birth, based on analysis of the TV images."

The fact that the North Korean leader even had a wife was only revealed in July last year when pictures emerged of a stylishly-dressed young woman accompanying him at official events.

Pyongyang's state media confirmed her identity later in the same month, in a rare move in the isolated and deeply patriarchal nation, which has rarely placed its first ladies under the spotlight.

According to intelligence reports cited by the South Korean media, the couple were married in 2009 and already have one child, although that has never been confirmed.

Ms Ri was described as coming from an ordinary family, with her father an academic and her mother a doctor. She visited South Korea in 2005 as a cheerleader for her country's squad in the Asian Athletics Championships.