Looking for an old scifi-movie i saw as little child, about 30 years ago

One scene i remember was that they where on a kinda desolate planet where they encounter small humanoids who turn out to be iradiated/mutated children . The children looked like they where wearing some kind ghillie suits. In the end a group of heroes enters the lair of the villain (called ‘the masters citadell’ if i remember right) One of them is captured and held down by two robots/androids/men in bulky spacesuits while a third one kills him with a rock. the remaining heroes reach the room where the villain is and defeat him and then get away before the citadell explodes. I know it’s not alot to go by but perhaps it still rings a bell