Islamist militants are increasingly funding themselves through kidnapping, with al-Qaida’s north African wing likely to have brought in tens of millions of dollars in ransoms in the past few years, a US treasury official has said. The US estimated that militant groups including al-Qaida in the Islamic Maghreb (Aqim) received $120m (£75m) in ransoms over the past decade, said David Cohen, undersecretary for terrorism and financial intelligence.