At least 10 people have been killed in a central Kenyan town after a police officer went on a shooting rampage in three different bars, before surrendering, officials have said.The shooting spree happened late on Saturday in the town of Siakago, located 150km northeast of the capital Nairobi.Police said on Sunday that they are investigating the shootings."He shot 10 people in bars in Siakago. Apparently he was looking for his girlfriend after he left duty," Charles Owino, a deputy spokesman in the regular police division told Reuters news agency."Among the 10 dead were two of his colleagues who were investigating the shootings."Munene Kamau, a journalist for the Kenya television network, told Al Jazeera that the killings sparked a mass protest early on Sunday outside the police station in Siakago.'No security'"These are furious residents demanding answers from the police as to how this incident happened," he said."In Siakago there is no security,'' Nyaga Manunga, the father of one of the victims, told the Associated Press."Someone can't just shoot 20 to 30 bullets without any reaction from the police."The officer is said to serve in a branch of Kenya's police system that is attached to its provincial administration which has its own chain of command separate from the regular police system.Antonin Newite, a local radio reporter, also told the Associated Press that the police officer openedfire in three different bars, killing one person in each of the first two bars and eight people in the third bar.He also said that many local residents did not realise what was happening because they mistookthe gunfire for fireworks.