Image copyright AP

Protesters have forced buses carrying migrant children and families to be prevented from reaching a processing centre in southern California.

People shouting slogans and waving US flags blocked three buses carrying undocumented Central American families to a border patrol station in Murrieta.

The migrants were flown to San Diego from Texas, where facilities report overcrowding after a surge in arrivals.

The Murrieta mayor had urged residents to complain about the transfer.

There were about 140 migrants on the bus, both adults and children.

They were sent to California to be assigned case numbers and undergo background checks before being released under supervision to await the deportation process, US immigration officials said.

"We can't start taking care of others if we can't take care of our own," said protester Nancy Greyson, 60, of Murrieta.

Image copyright Reuters Image caption Protesters were angry that illegal immigrants were being sent to their town

Image copyright Reuters Image caption Border Patrol agents kept a watchful eye on the protests

After the buses were blocked, federal authorities re-routed the buses to another centre, this time further south, close to the Mexico border.

The US government is also planning to fly migrants to Texas cities and another site in California, while some have already been taken to Arizona.

Many of them are fleeing violence and extortion from gangs in Guatemala, El Salvador and Honduras.

More than 52,000 unaccompanied children have been detained since October after crossing the Texas-Mexico border, in what President Barack Obama has called a humanitarian crisis.

He vowed this week to try and fix the "broken" immigration system and he said many migrants now coming misunderstand the rules and believe they will receive leniency from US authorities.