The official Xinhua News Agency said that the bus flipped over after crashing into a car in the port city of Tianjin on Friday afternoon, injuring 18 others.
Xinhua cited a Tianjin traffic official as saying the bus was speeding and that many passengers were thrown out of the vehicle when it hit the car and rolled over.
In eastern Anhui province, at least 10 people died and 19 were injured in a 24-vehicle pileup on an expressway as foggy weather reduced visibility, the Beijing News daily said.
Eleven people in a van were killed after a truck crashed into the vehicle in central Henan province, the newspaper said.
Serious traffic accidents are common in China due to often overloaded vehicles and poorly trained drivers who often ignore traffic laws.
Friday was the end of a weeklong holiday to mark China's National Day.