A distributed denial-of-service attack against the department's website -- www.oaklandpolice.com -- is underway, and the website currently is unreachable.
"The time has come to retaliate against Oakland police via all non-violent means, beginning with 'doxing' of individual officers and particularly higher-ups involved in the department's conduct of late," read an Anonymous statement, posted to Pastebin.
An Oakland police spokesperson could not immediately be reached for comment.
Doxing references the public release of information about individuals.
Anonymous' operation, dubbed "OpUprise," comes in response to the actions Tuesday night of Oakland police trying to squash a largely peaceful demonstration organized to protest the clearing of an encampment where Occupy Oakland members had been staying.
Police used tear gas, rubber bullets and flash grenades against the demonstrators, according to reports and video posted on YouTube. Authorities have said the response was warranted because some of the rally participants were throwing objects at them.
The most seriously injured victim was Scott Olsen, an Iraq War veteran, who suffered a fractured skull after being struck by a police projectile. His condition was upgraded to "fair" today, according to reports.
According to the Pastebin document, Anonymous is offering a "no questions asked" $1,000 reward for information about the officer who threw the projectile at Olsen.
The police's response led to much criticism of Oakland Mayor Jean Quan, who responded with a statement that expressed sympathy with victims and promise to decrease police presence around Frank Ogawa plaza, where some of the demonstrators, many of whom are protesting corporate influence in politics and the country's large wealth inequality gap, have been living.
UPDATE: The Oakland police website appeared operational again, as of Thursday evening EST.