Yes it could be physical strength, for sure. It's the simplest explanation.
But I speculate it's his magic, rather than his physical strength. He uses his 2 fingers to stop an attack, and the other hand can divert the attack.
He had to use magic to hurt Kagura (blue square) he didn't hit her.
It really seemed like the 2 finger thing was pointed out for us (top panel of the 2nd page) to demonstrate his magic Kinda like DiMaria clicking her teeth. Or, it could just emphasise his ridiculous strength.