A gunman has killed six people and critically wounded three more in a shooting spree at a hair salon in California.

Authorities said police have arrested a suspect in Wednesday's shooting, but they are not yet sure what the motive was. The suspect was detained after trying to flee the scene in a vehicle.

The victims have not yet been identified and it is not clear whether they were customers, employees or bystanders.

The salon is located in a shopping center along the Pacific Coast Highway, in a town called Seal Beach.