Some emergencies were "almost invisible", said Laurie Lee, interim secretary-general of CARE, which helps people hit by disasters and emergencies.
"As our report shows, 70 million people in the 10 least-reported major emergencies were suffering in silence," he told a news briefing.
Such emergencies account for one-third of the 220 million people in need of humanitarian assistance but received only two percent of the funding, he said.
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Among them are 70 percent of North Koreans who don't get enough food to eat and rely on government food aid, Lee said, adding: "That is 18 million people."
While an international spotlight has shown on North Korea's nuclear program and political tensions, little is known about the humanitarian situation there, the report said.
Two in five North Koreans are undernourished, the report said, citing United Nations statistics.
The leadership exacerbates the dire humanitarian situation in the isolated country, CARE said, along with global warming and frequent natural hazards, such as floods, rising temperatures or prolonged droughts.
Last July, North Korea experienced the worst drought since 2001, it said, with below-average rainfall in key areas for crop production severely disrupting planting and damaging the 2017 main season crops.
North Korean women and children are the most vulnerable, it said. More than 200,000 children are estimated to suffer from severe acute malnutrition, which can be deadly, the report said.