Kidnapped off the streets? I think for “bodies burned in pits” I might prefer “slaughtered” or “butchered”. Disappeared sounds rather light for what we’re currently discussing to my ear.

"Disappeared" does strongly imply that those people are dead, because that's what usually to happen to people that the government decides to kidnap.

But then, that's what usually happen to the people that the government decides to kidnap. So the OP's usage is perfectly correct, and the expectation that those people are dead should exist. Including the people that we know that were sent to the concentration camp, because despite nobody claiming it's an extermination camp the leading one does strongly tend to morph into the later.