SEOUL, Oct 8 (Reuters) - North Korea"s food situation remains perilous according to analysts and a United Nations expert who raised doubts this week about its harvest, and there are signs that it is receiving large shipments of humanitarian aid from China. North Korea has long suffered from food insecurity, with observers saying that government mismanagement of the economy is exacerbated by international sanctions, natural disasters, and now the COVID-19 pandemic, which prompted unprecedented border lockdowns there. The country typically relies on imports and aid from China to make up for poor harvests, but its strict self-imposed border lockdowns aimed at preventing a coronavirus outbreak have slowed trade to a trickle and cast doubts on its ability to overcome food shortages. International sanctions imposed over North Korea"s nuclear weapons programme cause additional hurdles, and should be eased to stave off a humanitarian crisis, a U.N. rights investigator said in a report seen by Reuters this week. Despite its economic woes, North Korea has continued to develop its nuclear weapons and ballistic missile arsenals, including testing a flurry of new short-range missiles in recent weeks, and building a major addition to its main nuclear reactor facility, which analysts said could be aimed at enriching more weapons-grade uranium. Much is riding on this year"s harvest after leader Kim Jong Un said the food situation was "tense." In July the United Nation"s Food and Agriculture Organization said the 2021 growing season appeared to be off to a good start, but a new report this week by a U.S.-based think-tank said data gathered by satellite point to a yield that falls short of an average or good harvest. "While not yet a crisis of famine proportions, the negative trend, combined with external factors such as low yields in the previous year and flood damage to the northeastern croplands and crop transport infrastructure, aggravate the food insecurity in the country," the Center for Strategic and International Studies said in a report released on Monday. For the first time in months this week there were signs that North Korea was accepting international aid, United Nations agencies saying some shipments had entered the country and were now in quarantine in North Korean ports. Health and nutrition supplies from the United Nations Children’s Fund (UNICEF), and medical supplies to support anti-pandemic work from the World Health Organisation were among the aid that had reached North Korea. The aid shipments have been pending for a long time, and don"t likely signal a broader opening of borders as North Korea has been letting in other goods for months, said Chad O"Carroll, CEO of the Seoul-based Korea Risk Group, which monitors North Korea. "North Korea has been letting other goods into the country since May, including large volumes of what appears to be humanitarian assistance from China," he said. China"s exports to North Korea rose for the third straight month in August, to $22.5 million. That was a fraction of the $219 million of exports in August 2019, before the pandemic lockdowns. O"Carroll said he thinks North Korea will still be able to stave off major food shortages through the aid and imports from China. "However, the quality, range and nutritional value of the food supplies on offer will be low," he added.