Washington - At least three police officers were shot in Louisiana on Sunday, officials said."Several officers were struck by gunfire," Baton Rouge police spokesperson Don Coppola told local television station WAFB."There are three they are describing as very seriously ill," Baton Rouge Mayor Kip Holden told the station, adding that more details will be forthcoming.The station aired video footage of police responding to the scene in Baton Rouge. Multiple shots could be heard as civilian cars quickly backed away.CNN reported a local source as saying at least seven officers were shot and three are feared dead. Some of the others are reported to be in critical condition, the station said.The shooting appeared to be carried out by a lone gunman carrying an assault rifle, local media reported."We think that the situation has been contained," Coppola said.Police arrested more than 100 protesters taking part in a demonstration against police brutality in Baton Rouge last week.Earlier in the month, five police officers were shot dead in Dallas - also by a lone gunman.