We went through something similar with our son who's now nearly 7 - aggressive bahaviour, delayed speech, disliking other children in his space. I was told that boys get surges of testosterone as they go through growth spurts, this can lead to bouts of aggressive behaviour. Here's what I found worked best:
Stay calm when he kicks off (easier said than done I know).
Be really clear about what is, and is not, acceptable behaviour.
Give warnings, then consequences, when he crosses the line (example - if my son deliberately hurt another child in the park, we went home immediately).
Don't threaten something you're not really going to follow through on.
Be consistant in how you manage his behaviour (discuss strategies with others who care for him).
Praise the positive behaviour (this is so important but really easy to overlook), make a big fuss of him when he behaves in a way that you want to encourage.
If you want to discuss his behaviour with him, only attempt to do so when he's calm.
I went on a brilliant parenting course based on 'The incredible Years' book by Caroline Webster-Stratton.
If this phase shows no sign of abating then seek some help. My son's just been diagnosed as ASD (autistic spectrum disorder) - I am not suggesting that this is the case with your son, as in normal development boys often go through the phase you have described.