At least 44 worshippers have been shot dead at a mosque in northeast Nigeria, reports say.The killings reportedly took place during prayers on Sunday morning, although news only emerged on Monday.The attack took place in Konduga in Borno state, 35km (22 miles) from the state capital Maiduguri.It is not clear who was responsible for the shootings. The Islamist group Boko Haram has killed thousands in northern Nigeria since 2009.