At least 10 people have been killed in a massive explosion that hit a United Nations building in Nigeria's capital, Abuja, leveling at least one complete wing of the structure. At least 10 people have been killed, while nine others have been reportedly injured, after ablast struck the UN building near the US Embassy on Friday just before 11 a.m, AP reported. Local police spokesman Jimoh Moshood confirmed the blast and said the cause of the explosion remains unknown. Witnesses say police are still searching the scene of the blast for victims. The developments come as the Boko Haram group has increased attacks on government targets since Nigerian security forces killed their leader, Mohammed Yusuf, while he was in custody in 2009. The group is blamed for bomb attacks and shootings in the northeast of the country. According to the Brussels-based International Crisis Group, ethnic and religious conflicts in Nigeria claimed the lives of over 14,000 people between 1999 and 2009.