A United Nations panel for child rights says North Korea is punishing children for their "parents' crimes" or political views by discrimination and urged Pyongyang to end child labour.
The UN Committee on the Rights of the Child, which reviewed Pyongyang's record last month, also voiced deep concern at what it said was the "ideological indoctrination" in its education system.
Tensions in the region and beyond, especially with the United States, have spiked considerably in recent months as North Korea conducted a series of tests of its medium- and long-range ballistic missiles, some of which flew over Japan, as well as its sixth nuclear test on September 3.
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In its findings, the panel said it remained concerned that North Korea did not "adequately guarantee the right to freedom from torture and other cruel or degrading treatment or punishment, in law and in practice, in particular of children forced to return to [North Korea], children living in street situations, and children in detention facilities, including political prison camps".
The UN panel, in a session on September 21, asked the North Korean delegation how "songbun", a system ranking citizens based on family loyalty to the ruling dynasty, affected children's access to education, health and food.
The North Korean delegation replied that this was an "imaginary concept" invented by hostile forces.
The watchdog, composed of 18 independent experts, also called on North Korea to allow children freedom of expression, including access to the internet.
North Korea told the UN panel last month that international sanctions imposed on it over its nuclear and ballistic missile programmes would endanger the survival of North Korean children.
The UN Security Council has unanimously imposed nine rounds of sanctions on North Korea since 2006, the latest last month capping fuel supplies to the isolated state.
The UN experts noted that economic sanctions had "repercussions on children's enjoyment of their rights".