A gang of armed robbers numbering more than 20 on raided four commercial banks in Sagamu area of southwest Nigeria\'s Ogun State, carting away an unspecified amount of money, police and bank sources reported on Friday. The robbers, who had sent an advance notice to strike in the area, had earlier made three unsuccessful attempts in the last three weeks to operate in the area. The robbers stormed the Sabo area of Sagamu around 11 a.m. local time on Thursday and started shooting sporadically into the air for about 15 minutes to scare residents away. They were said to have eventually forced their way into the branches of Guarantee Trust Bank, Diamond Bank, Skye Bank and Zenith Bank. The hoodlums used explosives to force the vaults of the banks open and carted away huge amounts of money. Sources said an attempt to rob the Intercontinental Bank branch in the area, however, met with stiff resistance as members of a vigilance group engaged the robbers in a shoot-out. Some residents caught in the shoot-out, which lasted for about 15 minutes, were said to have been injured and rushed to the state Teaching Hospital in Sagamu. The robbers were said to have escaped through Iperu/Ago-Iwoye road as some students made unsuccessful attempts to stop them. The robbery incident, which lasted for about two hours, paralyzed commercial activities in the area as residents and shop owners shut themselves in. The incident was coming exactly two weeks after three people were killed in a similar bank robbery operation at Ago-Iwoye in Ijebu-North Local Government Area of the state. State police spokesperson Muyiwa Adejobi confirmed the incident to reporters, but decline to give further details.