SEOUL, Jan 13 (Reuters) - After nearly two years of border closures to protect North Korea against the pandemic, some humanitarian aid is trickling into the country, though shipments of key supplies including food remain blocked, according to United Nations organisations. The United Nations children"s agency UNICEF said this week that at least two of its shipments of nutrition and tuberculosis treatment supplies were released after up to three months of quarantine. "The first of these consignments of UNICEF supplies has now been cleared from disinfection at the port of Nampo and released to the government distribution centre ready for allocations to health and nutrition facilities," spokeswoman Caroline den Dulk told Reuters in an email. The moves were first reported on Friday by Seoul-based NK News, but den Dulk did not elaborate on exactly when the shipments were released. North Korea has not reported any COVID-19 cases and has imposed strict anti-virus measures, including border closures and domestic travel curbs since the pandemic began early 2020. The U.N."s special rapporteur on human rights in North Korea has said the country"s most vulnerable people were at risk of starvation after it slipped deeper into isolation during the COVID-19 pandemic. North Korea called that report "slander," but leader Kim Jong Un has admitted to a "tense" food situation. Since August 2021, "very few relief items" were permitted to enter North Korea, after undergoing a quarantine period of more than three months followed by disinfection procedures, the World Food Programme said in its December report on North Korea. WFP said after North Korea closed its borders in early 2020, the organisation continued to distribute food stocks already in the country, until the last of the stocks was distributed in March 2021. "The closure of borders for food and people and restricted mobility within the country remain the key challenges," the report said. "There is currently no clear timeframe for reopening the border." The World Health Organization (WHO) said in October that COVID-19 aid supplies had arrived in North Korea but were being held in quarantine at Nampo. WHO representatives did not respond to a request for updates on the status of those supplies.