In Zhengzhou, central China, police arrested "thugs" who Thursday night damaged street installations and overturned a vehicle.
There have also been arrests in Xian, Canton, Changsha, Zhengzhou and other cities.
The Sichuan and Beijing trials followed another mass execution in Zhengzhou, central China, on Saturday, when 11 train robbers were put to death.
Two girls from Sichuan province, one 15 years old and the other 16, were on their way home after visiting relatives in Zhengzhou when they were abducted at the Zhengzhou railway station.
Two girls from Sichuan province, one 15 years old and the other 16, were on their way home after visiting relatives in Zhengzhou when they were abducted at the Zhengzhou railway station.
More than 200 grain trading companies were to begin dealing on opening day at the Wholesale Grain Market in Zhengzhou, the provincial capital of Henan, China's wheat heartland, the official Xinhua News Agency reported.
Thirteen other people were injured in the crash Monday near the provincial capital of Zhengzhou, the China Daily said.
Along the river near Zhengzhou, where the soil was once too alkaline to produce anything but salt, irrigation has made the rice paddies the most productive in Henan.