SUBALPUR, India—When the elders in this small Hindu farming village discovered last month that a local woman intended to marry a Muslim, their reaction was swift and savage.

The village chief and 12 others dragged the 20-year-old woman to a shed and gang-raped her, the local police allege. She and her suitor were then tied to a tree overnight, witnesses say, and the village council fined them the next day.

Such...