"I don't know what is happening in North Korea, but I found many parasites when examining other defectors", added Professor Seo Min.
Defense Secretary James Mattis on Thursday indicated that a recent halt in North Korean nuclear and missile testing may signal an opportunity for talks, though Pentagon officials cautioned that it is too soon to read into the pause.
38North also cites the continuous movement of parts in and out of yards next to construction halls at the shipyard and the presence of a stand used to test the mechanism that launches missiles from a submarine.
Yonhap noted in a story on Friday that Joseph Yun, the top USA nuclear envoy, indicated earlier this week that if North Korea halts nuclear and missile testing for about 60 days, that it might be the signal that Washington needs to resume direct dialogue with Pyongyang. The World Food Programme (WFP) says a quarter of North Korean children from six-months to almost five-years old, who attend nurseries that the organisation assists, suffer from chronic malnutrition. It said these appeared larger than those for North Korea's Romeo-class attack submarine.
On July 4, North Korea launched its first test of an intercontinental ballistic missile in an attempt to come up with a powerful weapon that could reach "anywhere in the world".
Mattis did not give any reasons for why North Korea hadn't recently undertaken tests, but said the Pentagon was closely watching the country, Reuters reported.
Between January and September, China exported almost 49,000 tonnes of corn to North Korea, compared with 3,125 tonnes in 2016, according to figures from Beijing.More news: UCLA Basketball Players Thank President Trump as They Return to US Soil
Trump has previously called negotiations with the isolated nation a waste of time.
North Korea has said it can not abandon its nuclear programme, which it says is necessary as a deterrent to a U.S. threat.
Yonhap, citing unidentified diplomats in Beijing, said there was a good chance that Mr Song would meet Mr Kim tomorrow.
Lee Min-bok, a North Korean agriculture expert, said: "Chemical fertiliser was supplied by the state until the 1970s, but from the early 1980s, production started to decrease".
It's been about nine weeks since Pyongyang conducted its last missile test - a Hwasong-12 intermediate-range missile test near Japan on September 15.
"The United States should abandon its hostile policy toward North Korea".
"As long as there is continuous hostile policy against my country by the U.S. and as long as there are continued war games at our doorstep, then there will not be negotiations", the ambassador said.