when your son hits somebody use a furm voice and look him in the eyes so he knows you are serious. tell him if he hits somebody again he will go in time out. timeout should be evey minute of his age. so he is 2. he should have two minutes time out. if he runs away from his timeout place dont look at him or speak to him just put him back. keep doing it until he stays there for two minutes. once he has stayed on timeout for two minutes tell him again why he was in time out. then tell him to say sorry to you. then give him a kiss and a hug.it is hard work but it does work. tell me how you got on. good luck.
Try going somewhere that will take that aggressive energy and use it for running, climbing, jumping and all, not just standing around or playing quietly. When you discipline him, do it without any physical force. Use depriving him of a favored treat or toy, and time out. If he sees you (or another important adult in his life) using force, he will feel that is the way to go. He is probably hitting because he is nervous, and yes, it is typical at this age.
Many 2 year old's go through this phase , in America we call it the terrible two's and it really exists, I am pretty certain he will out grow it,I have always liked the time out theory and I think you should continue with the firm No so he knows what he is doing is bad. Make sure he has social activities with children on a regular basis as sometimes the children that are not too social do not know how to handle other kids when they meet them ,if you know other parents try to have playdates or park meetings so he gets used to them .It will pass..good luck