A Muni passenger punched a woman who littered on the bus Tuesday, police said.

The litterbug was not seriously hurt. She called police around 10 a.m. saying she was assaulted in the area of Mission and 30th streets.

The woman admitted to police that she had left an empty bottle behind on the bus when she exited. That angered another passenger, who yelled at her for littering and then hurled the bottle at her, police said.

The woman stormed back into the bus to confront the passenger, but was punched in the face. During the assault, she reached for her phone but learned it had fallen to the ground. The angry passenger picked the phone up, handed it to the woman, and then asked if she wanted to keep fighting.

The woman told her she was calling police, but by the time cops came around the passenger was gone.

maldax@sfexaminer.com