How can i detect collision in melee combat?

Hi to all

In my game i have two group of ai characters(i.e. red and blue)and red ai could attack to blue’ npc’s have a “charactercontroler” component and their attack animation is melee type such as punching or Spurn attack without any weapon.Since my npc’s collider is a capsule like(charactercontroler)and their hand or leg dose not had collider,how can i detect colliding with other npc’s?

I try adding a separate collider(capsule collider) to their hand and leg,but it did’nt work.

any suggestion or help would be appreciated.
excuse me for my bad english.

Well why don’t you just add more colliders?

For future readers:
I add some empty gameobject to npc’s hand and foot and added capsule Collider’s to them and use oncollisionEnter for detecting collisions and modify npc health.
For solving weird npc movement i enable all X, Y and Z parameters of Freeze Position and Freeze Rotation in Constraints of rigidbodies(i leave “IsKinematic” and “use gravity” fields unchecked).
here is my collision detection script:

     void OnCollisionEnter(Collision collision) 
        int dmg;
			 	collision.gameObject.GetComponent<AIHealth>().SetAIHealth(- dmg,0)	;
		Debug.Log( " is damaged by "+name+" by damage "+dmg+"time:"+Time.time);
			Debug.Log("collided with: "" and not attacking");