17 month old started hitting

[Newmum26]

DS has started to pick up his toys and hit me and DH with them thinking it's funny and looking you in the eye as he does it for a reaction.
I tried quietly just saying 'No' and he kept doing it so I've tried shouting 'No' and it still doesn't stop him he just finds it funny and only stops if we really shout at him No!! Then he burst into tears and launches himself at us for a cuddle 🙁
So hard to know how to deal with it what would you advise? And is it a phase where he's testing how far he can go? Will it pass?!
Thanks ☺️