Mystery surrounds the whereabouts of the new bride of Kim Jong-un, with reports suggesting that she has fallen foul of the old guard in the North Korean regime for failing to wear a lapel pin.

All North Koreans are required to wear the badge, featuring the face of Kim Il-sung, as a mark of their loyalty to the founder of the nation.

Ri Sol-ju, formerly the lead singer with the Ponchonbo Electronic Ensemble, was only officially unveiled as Kim's wife in July but had previously been pictured accompanying the "Young General" on his visits to state-run farms, military units and official ceremonies.

Initially, state media missed no opportunity to play up the regime's new First Lady, showing her at a gala in July wearing a black trouser suit and carrying what appeared to be a Chanel bag.

Ri's appearances marked a major departure from traditional images of North Korean women, who are generally expected to wear skirts or baggy, Mao-style work clothes in shades of grey or brown.

She may have gone too far, however, by replacing the Kim lapel badge with more feminine flowered brooches.

South Korean media have reported that Ri has not been seen in public for 40 days, giving rise to inevitable speculation about her fate.

Commenting that in pictures of Ri without the all-important Kim badge that she looked "confident," the NK News web site suggested that her fashion choices "may have riled some of the older and more conservative figures within the leadership."

Another web site claimed that senior members of the ruling Workers' Party had identified a "lack of dedication to the Kims" and declared this was "completely unacceptable, with repercussions to ensue."

Analysts have suggested that the new leadership is attempting to soften its image with the public and raise their living standards, although the failure of a senior member to show due deference to the founder of the nation could threaten the structural integrity of the regime, they said.

An alternative theory that has been put forward is that Ri has dropped out of the limelight because she is pregnant.