A top North Korean finance official has been sacked following a chaotic currency revaluation that has triggered increased food shortages and social unrest in the country, news reports said Wednesday.

Pak Nam-Ki, the communist party's director for planning and finance, has been absent from public activities since early January, according to a spokesman for South Korea's spy agency, the National Intelligence Service.

"We are closely monitoring the North to find out the reason why," the spokesman told AFP. "But we have yet to confirm if he has been sacked or not."

South Korean news reports said Pak was dismissed after the redenomination resulted in runaway inflation, worsening food shortages and sporadic violence in the tightly controlled state.

"Mutual recriminations are rampant within the North's power circles over the failure of the redenomination (and) Director Pak, who led the reform, has been sacrificed," a diplomatic source in Beijing told Chosun Ilbo newspaper.

Yonhap news agency, quoting traders in the Chinese city of Dandong near the North Korean border, said Pak had been sacked and was awaiting trial.

Under a November 30 decree, old banknotes were swapped for new at a rate of 100 to one. But the amount that could be exchanged was restricted, effectively wiping out many people's savings and causing popular anger.

The revaluation was apparently an attempt by Kim Jong-Il's regime to reassert state control over the economy and restrain growing free-market activity, as well as to curb rising prices.

But it reportedly backfired, wreaking havoc with distribution networks and sparking inflation and chaos in shops and markets. Some people were said to be bartering goods to survive.

Organisations with contacts in the North have reported some attacks by angry North Koreans on security agents patrolling markets.

National Intelligence Service chief Won Sei-Hoon has been quoted as saying that the revaluation sparked riots but that the government appeared now to have them under control.

"Had the revaluation been a success, North Korea would have ascribed it to the leadership of Kim Jong-Un, third son of the current leader, and used it to justify a third-generation succession," the source told Chosun.

"Dear Leader" Kim Jong-Il, who himself took over from his father, is widely believed to have picked Jong-Un as his eventual successor.

The new won's value has been falling sharply against foreign currency, Chosun quoted traders in China as saying.

At the outset of the revaluation, one US dollar fetched 98 won. Currently, it is exchanged for somewhere between 300 to 500 won, according to the traders.

Economics professor Kim Byung-Yeon of Seoul National University told a seminar on Tuesday that because of the revaluation's failure, the North would have to ease restrictions on private markets, which began cropping up in 2005.

A survey of 200 North Koreans who defected to the South in 2007 and 2008 showed some 76 percent took part in private economic activities, he said.

North Korea has suffered severe food shortages since a famine in the 1990s killed hundreds of thousands.

The United Nations World Food Programme, citing a survey, said last September that a third of the country's women and young children were malnourished.

Kim Jong-Il has vowed to end his people's dependence on corn and feed them more rice and wheat products instead, state media reported Monday, in a rare acknowledgment of his regime's failure to improve living standards.