Can tugging on your stomach hard cause internal bleeding?

You may have: Superficial bleeding in the subcutaneous fat which is highly vascular. However internal bleeding would only result under conditions such as extremely rough sex with grabbing of the skin to maintain a grip on your partner, or grabbing the abdomen with such force that internal organs such as the spleen are lacerated (don't laugh I've seen this in real life). A detailed mechanism of injury would help

Depends: Who did it? With what? And why? It would be tough to do, and if was enough to cause internal bleeding unless the person had a bleeding disorder or other debilitating illness, In an adult it would have to be done with a whole lot of force and it would hurt so much that you would probably be at an ER to be treated. It depends on the victim too, babies and kids are easier to hurt. sad to say.