It was recently revealed (by commercial satellite photos and other reports) that an April 2016 test of a North Korean Hwasong-12 IRBM (Intermediate Range Ballistic Missile) had not only failed (as was reported soon after the missile launch) but that the missile, still containing much of its liquid fuel, landed in the industrial outskirts of Tokchon, a city of 200,000 people about a hundred kilometers northeast of the capital Pyongyang. The Hwasong-12 was launched from a military base 65 kilometers north of Pyongyang and the missile landed 38 kilometers northeast of the launch site and caused considerable damage on the ground. Any casualties would be considered state secrets in North Korea and it may take a while for the facts to become known.
Liquid fueled missiles can cause enormous damage if they explode on the ground with much of their fuel still on board. The most extreme such accident took place in Russia during a 1960 test of its new R-16 (SS-7) ballistic missile at the remote Baikonur Cosmodrome in Central Asia. This missile was about twice the size of the Hwasong-12 and exploded on the launch pad, while fully fueled, as a senior Russian official overruled existing safety rules and ordered technical personnel to fix a problem with the missile that was fully fueled but was experiencing some technical delay to an important test launch. There was a short circuit in the rocket engine that ignited the fuel and the explosion killed over 120 people. There were other missile accidents at Baikonur over the years as failed launches of missiles (military and for satellites) dropped large pieces of missiles in the area. There was some damage and a few casualties, but that was mainly due to the fact that the area around Baikonur was always sparsely populated.
In the early days of ballistic missile testing (for use as weapons or putting satellites into orbit) it was noted that even successful launches often had a first stage fall back to earth and it would probably be safer to put these launch sites on the coast so the rockets could be sent out over open water. North Korea is a small country and insists on some of its launch sites being inland, in the midst of farms and urban areas. Accidents were bound to happen as more tests of larger rockets were conducted. Russia has been moving a lot of its large rocket launches to new coastal facilities. China still uses inland launch sites but has vast tracts of interior territory that is either desert or simply not occupied by many people. Even with Baikonur there was very little damage or casualties on the ground outside the launch site. But once the Soviet Union dissolved and Baikonur became the property of the new state of Kazakhstan any accidents outside the launch site that damaged property or caused any injuries to people or livestock were big news and a political issue. So Russia moved most of its launches elsewhere. North Korea does not have that option so unless it moves all these long range, multi-stage rocket tests to coastal sites there will be more incidents of North Korean property, and people, crushed beneath things that unexpectedly fell from the sky.