Updated

Oakland police say at least 45 people were arrested following a largely peaceful protest against police killings.

The arrests came toward the end of a day when thousands of protesters took to the streets of San Francisco and Oakland on Saturday to join in a national demonstration against the killings of unarmed black men by police.

Oakland police spokeswoman Johnna Watson says that hours later a crowd of about 500 remained.

She says police arrested at least 45 people for crimes such as vandalism, failure to disperse and resisting arrest.

By midnight Saturday there were no reports of any protest activity in Oakland.

Earlier in the day, protesters on both sides of the San Francisco Bay carried signs that read "black lives matter" and chanted slogans and songs about opposing police brutality.

Several other cities across the United States experienced demonstrations Saturday.