The victims were in the parking lot at 1 Sunvalley Blvd., in front of the Sears store, when a group of six to nine girls "jumped" them shortly before 6:30 p.m., Cerletti said.
The girls were not armed, but allegedly punched and shoved the victims and stole a purse.
The victims were able to describe two girls who appeared to be leading the attack and police sent notice to neighboring police agencies to be on the lookout for the suspects.
A short time later, police received a call from a witness who claimed to have seen the assault and followed the girls to a home on Diablo Court in Pleasant Hill, Cerletti said.
Concord police went to the home and found six female juveniles. The victims and the witness identified two of the girls as the main assailants, Cerletti said.
The girls were arrested and booked into Juvenile Hall in Martinez on suspicion of strong-arm robbery.