Protesters have taken to the streets in southern California following yet another police shooting of an unarmed African American.

It came after police shot and killed Ugandan-born Alfred Olango, who suffered a mental disability.

The two officers involved were responding to several calls as the victim was walking in traffic in the San Diego suburb of El Cajon.

Police say the man pulled an object from his pocket and took aim at them in a "shooting stance". However, no weapon from the man was recovered at the scene. The object he was said to be carrying was not specified.

Protesters have yelled "murder" and demanded a federal investigation into the fatal shooting.

"We tried the whole Martin Luther King way, you know, now it's time for us to get the Malcom X way, we've been quiet, we've been silent and we're tired of sitting back and letting you guys kill us just because we're black," said protester.

"It ain't just black people, it's everybody. We need to get this shit changed. We need the police to understand that we matter, lives matter. It's not indiscriminate killing, we need the cops to get punished for what they do. We need to make a stand y'all," said protester.