IMPHAL, April 3: Unidentified militants have forced closure of three schools here for allegedly not paying ransom money, official sources said today, reports PTI. Sources said the Little Flower High School, St Joseph's School and St George School have been closed down for an indefinite period following the demand for payment of huge amount from some underground organisations. School authorities have notified that schools would remain closed until further orders without showing reason. Sources in the schools said that some valley-based insurgent outfits had demanded huge amount from the institutions. The militants had forced closure of Little Flower School about a month ago on the same ground.