Federal riot police ended their weeks-long occupation of the center of the Mexican tourist city Oaxaca on Saturday, having weakened a protest movement trying to oust a state governor. Violent clashes between the masked activists and riot police, and a string of shootings of protesters, made Oaxaca one of new President Felipe Calderon's top problems. But the arrest of several high profile protest leaders has weakened the movement against the governor, and the frequency and size of demonstrations has fallen. The federal police boarded trucks and rolled out of the city before dawn, handing over security to state police. The federal agents were headed for a nearby air base where they would remain until further notice, a state spokeswoman said. "It's no longer necessary that they guard the streets; we are doing it now," said state government spokeswoman Luz Divina Zarate.