It might be a mortar. But the fins (four of them are larger than the diameter of the body. That would be unusual.
It's about the right size to be a Kornet-like anti-tank thing. But the back end is a bit too skinny for a decent rocket motor.
It's the right configuration to be a very tiny unguided bomb. But I wasn't aware they make them that small.
So I don't know what it is. Maybe some mexican got his hands on something like a 120mm mortar (closest thing I could find, still not a match, pic related) and got artistic with aftermarket fins.