At least 11 people were killed on Monday in a twin suicide bombing in Nigeria's city of Potiskum, hospital sources said.The attacks are suspected to be carried out by two Boko Haram suicide bombers, with one on the office of a civilian security group set up to defend local people against such attacks and another on a pub, said a senior medical staff who preferred to be anonymous, Xinhua reported.At least eight others were injured and are receiving treatment, the doctor added.The first blast happened after the suicide bomber ran into the building where the civilian security group is located, and the explosive devices were wired round his body, witness Abubakar Salisu said.One of the security group's commanders identified as Alhaji Ado was among the dead, Salisu added.Few minutes later after the first blast, another suicide bomber hit a pub in Daurawa area of the city, killing mostly patrons of the bar, another source said.Potiskum, the largest commercial town in Yobe state, has recorded several deadly attacks in the past.