This "needle bombs" are called also "ball-bombs", cassete bombs with ball elements, with killing particles (ball-bearing steel balls or other things) molded (wrong word probably) inside the shells. I have seen such things recovered from Vietnam in our department museum in college.
I don't know if they were prohibited by international conventions, but I don't know if they were manufactured in USSR, so Estel probably had no experience using them.
Anyway, bombing apartment blocks with cassete weapons is beyond my comrehension. It's inhuman.