A computer programmer in Christchurch is creating headlines around the world after discovering that North Korea has deleted thousands of news articles mentioning Jang Song Thaek, the former top government and party official, who was executed Thursday.

The discovery was made by Frank Feinstein who tracks North Korea's media output for a Washington website, NK News.

It has been picked up by major news outlets around the world.

NK News says Feinstein discovered that the Korea Central News Agency (KCNA) has deleted more than 35,000 articles from its on-line archives.

The deletion, the biggest ever article removal in KCNA's history, means that with the exception of a small number of articles about Kim Jong Un, the digital record of state-approved news about him reaches back only to October 2013.

"There were 35,000 articles dated September 2013 or earlier on KCNA in Korean," Feinstein says.

"If they're leaving the odd one in, it's still a kill ratio of 98-99 percent."

In addition to the 35,000 original Korean language articles, translations in English, Spanish, Chinese and Japanese were all removed from the archives, bringing the total to nearly 100,000 deleted articles.

NK News quotes Feinstein saying that about 20,000 articles had also been removed from the archives of the Rodong Sinmun, North Korea's state newspaper.

"This is a calculated thing they've done," he said.

"Across all sites, it means the order most likely came from above each individual agency.

"This is what makes it so interesting - it's a true North Korean purge, not just a KCNA one."

NK News quoted a North Korean expert, who did not want to be named, saying it was an extreme action.

Feinstein said he could not tell at the moment if the mass-deletion was permanent, but he added: "North Korean websites have recently explored ways to reduce the permanence of their electronic footprint with Google. This, when viewed with other data, suggest it is likely these changes are permanent."

- Fairfax Media