One police officer was slashed by a razor and another had his uniform torn and cheek cut in a clash with "Occupy San Francisco" protesters Saturday afternoon, police said.

The confrontation happened at around 3:30pm local time, as police attempted to prevent marching demonstrators from blocking a downtown intersection, the Contra Costa Times reported.

A female protester emerged from the crowd with an "exacto razor blade attached to a pen or pencil-like object," San Francisco police said.

"The female slashed the inside of the officer's hand and ran back into the crowd before the officer had time to realize he was cut."

In a second incident, a protester grabbed an officer's police radio and ran back into the crowd. As the officer attempted to retrieve it, a second protester blocked the officer and tore his uniform and cut his cheek, police said, suggesting a weapon was used.

Both injured officers were treated and released at the scene.

No one has been arrested.