Two teenage girls wearing suicide belts blew themselves up in a market in northern Nigeria on Tuesday, killing at least 40 people, authorities said. It was the latest in a string of horrific attacks in Nigeria for which Islamist militants are blamed, and there has been little response from the Nigerian military. The latest attack took place in the Borno state capital of Maiduguri. The head of a community vigilante militia in the city said the first girl detonated hidden explosives, killing about three women. When a crowd gathered, the second teen blew herself up, killing dozens. Female suicide bombings are relatively rare in Nigeria.