These were "mines" used to blow up bridges, roads and railroads. The bigger ones had thousands of kg of explosives. So more like remote demolition over radio. I

These were "mines" used to blow up bridges, roads and railroads. The bigger ones had thousands of kg of explosives. So more like remote demolition over radio. Idea being that you could destroy the critical infrastructure after retreating from the area and if you had vision on it when someone was on it like the first one that killed a couple officers (killed a major who was the chief lawyer for the Finnish General Staff) Modern equivalent would be cellphone bombs in roads in Afghanistan/Iraq.