NIAMEY, Aug 25 (Reuters) - Hundreds of Boko Haram militants attacked a military post in southern Niger overnight, killing 16 soldiers and wounding nine more, the defence ministry said on Wednesday. About 50 of the Islamist militants were killed in the resulting combat in the West African country"s Diffa region and significant quantities of weapons were recovered, the ministry said in a statement. The Boko Haram insurgency broke out in northeastern Nigeria in 2009, but violence frequently spills over into neighbouring Chad, Niger and Cameroon in the Lake Chad Basin. In December, an attack blamed on Boko Haram killed 28 people and burned 800 homes in the Diffa region.