Gunmen kidnapped 317 girls from a boarding school in northwest Nigeria, police said in a statement Friday, the latest in a rising tide of high-school abductions across Africa’s most populous nation, where kidnapping for ransom has become a lucrative industry. Armed militants broke into the Government Girls Secondary School, Jangebe in Zamfara state at around 1 a.m. Friday and packed schoolgirls onto vehicles or walked them toward the nearby Rugu forest, which spreads over three states and hundreds of miles. By morning, community leaders were still working to tally the number of people missing. Ahmad Abdullahi, a parent, said that his daughter had escaped, but that five of his nieces, between 14 and 17 years old, were among the missing. The abduction is the second in a little over a week in Nigeria’s northwest, where a surge in armed militancy has led to a worsening breakdown of security.