At least 29 people, including young children, have been killed in an attack on a camp for displaced people in Myanmar’s Kachin state, according to media reports and two local activists. Dozens more people were injured in the attack, which happened at about 11.30pm on Monday night in Kachin, Myanmar’s northernmost state, it was reported. Unverified images on social media, showed men carrying victims, including a small child, from the rubble in the darkness. The Kachin Independence Organisation (KIO), a political group that has long sought greater autonomy for the Kachin ethnic minority, said 29 people had been killed and 57 injured. This included 11 children under the age of 16. It said the attack was from heavy artillery, not an airstrike as some had previously suggested. Estimates of the death toll have varied. A Kachin activist based in Laiza, who spoke anonymously, earlier told the Guardian 33 people had been killed, including 13 children. A three-month-old baby was among the victims, she said. She added that the death toll could rise further because the camp covered a large area and volunteers were still recovering bodies. Homes in the camps were built on mountains, she added, and so houses had become buried under the soil. “Houses in the camp are very closed to each other, so the situation is totally messed up,” she said, adding that the attack was only the latest of the military’s “inhumane acts”. “There are many cases like this. This is not the only case,” she said. The attack took place at Mung Lai Hkyet IDP camp, a few kilometres from a military base run by the Kachin Independence Army (KIA), the military wing of the KIO and one of many groups fighting against Myanmar’s military junta, which seized power in 2021. The area, near the border with China, has been the scene of frequent armed clashes over recent months. The UN has warned of limited humanitarian access in Kachin state and many other areas of the country, describing a dire level of need. A second Kachin activist based in Laiza, who spoke to the Guardian from a hospital treating the injured, said: “The whole block of the camp has disappeared. It is like a big hole has been left in the earth, and houses were smashed. “My house is around six miles away from the Mung Lai Hkyet IDP camp. But my house was also shaking. The ceilings and doors of houses in Laiza collapsed.” She was at the hospital helping doctors with logistics but said she could not bring herself to look at the victims. “I can’t be emotional as I need to continue working,” she said. “I saw three young kids who lost their mothers. I do not dare to look at the kids.” Gen Zaw Min Tun, a junta spokesperson, denied the military was responsible. He told military-controlled TV that the junta had analysed the incident and believed that the explosion was caused by bombs that had been kept in storage by the KIA. The KIA could not immediately be reached for comment. The military has frequently been accused of striking civilian sites, including hospitals, schools, religious sites and civilian homes. Last year, the military killed 60 people, including musicians and children, in an airstrike that targeted a concert in Kachin. The attack took place on the same day that Myanmar’s ambassador to the United Nations, Kyaw Moe Tun, told a UN committee that, since the coup, the military has imported more than $1bn-worth of arms and raw materials for a “scorched-earth policy that has murdered more than 4,000 civilians including women and children, forcibly displaced around 2 million and destroyed or burned down over 75,000 homes”. Kyaw Moe Tun – who has remained loyal to the civilian government and does not represent the junta – cited data from researchers that indicated there was an average of 30 airstrikes a month in Myanmar from January to June this year, and urged member states and the security council to impose comprehensive arms embargos against the military. Since seizing power in February 2021, the military has faced determined opposition from an armed resistance, which includes both armed groups that formed after the coup, and larger, established armed groups such as the KIA. The KIA has offered sanctuary to protesters, politicians and others fleeing military abuses, and has trained fighters from newer groups that oppose the coup. The Mung Lai Hkyet IDP camp was set up in 2011 when a ceasefire agreement between the KIA and the military, collapsed. It has grown in size since the coup, however, as growing numbers of people have been displaced and is home to about 850 people. The conflict has forced 2 million people to flee their homes, an unprecedented number in the country, according to the UN, caused soaring poverty and the collapse of education and health services. Aung Myo Min, the minister for human rights in Myanmar’s national unity government, which was set up in opposition to the junta, said the military was committing war crimes, and with more cruelty. “But there are countries still selling weapons to them,” he said. “Now is the time for them to understand that the weapons that they sold to the junta are killing innocent children and people.” Russia and China are the main suppliers of advanced weapons systems to the Myanmar military, according to a UN report published earlier this year.