Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: In an embarrassing blow to its perception from an increasingly skeptical public, the Nigerian military Thursday retracted a report that nearly all the 129 school girls kidnapped by suspected Boko Haram militants had been released. Just hours after a parent of an abducted girl claimed the Defense Ministry lied Wednesday about all but eight girls finding freedom, the director of defense said the initial report was "not intended to deceive the public." Maj. Gen. Chris Olukolade's statement didn't indicate how many of the girls were still unaccounted for. "The number of those still missing is not the issue now as the life of every Nigerian is very precious," it said.Parents accuse the military of lying about the number of girls who are freeOne father says it's only 14 of 129; official says at least 30 girls escapedMilitary continues to search forest in northeast Nigeria, official says 
 Question:Armed militant groups in Nigeria's northeastern region are nothing new, but _ has taken the violence to unprecedented levels since 2009.

Boko Haram