Killing dolls

China has introduced new deathly machines to warzone, killing dolls. These wandering little robot mines and assasins are cheap to product in masses and when dropped to combat zone, they soon make the area unhabitable by killing all humans. They have small blowgun for poisoned needles and in their small nanolaboratory they have receipts for several dozens deathly poisons for whatever substances they can find. With their sunpanels and batteries they can go forever. When forced to stop they blow off their selfdestruction charge. If they are trapped to box they soon find that out and....
But Afghan troops finded way to fool them by catching several of them to doughnut shaped pipe!

When examined several months, scientist found out "easter egg". Every 13. day of friday night some dolls randomly gathered and danced american line dance together and singed:
"I'm just a sneaking, leaping, reaping, shooting, killing doll...." (You can make more lyrics yourself)
This explained some odd reports of english singing little demons dancing in the deep forests.....