New York police are eating extra helpings of humble pie after asking people to post images of themselves and NYPD officers on Twitter - only to face a deluge of pictures of alleged police brutality.

"Do you have a photo w/ a member of the NYPD? Tweet us & tag it #myNYPD. It may be featured on our Facebook," the department posted on its NYPD News Twitter feed, hoping to fuel a feel-good, low-cost public relations campaign.

The result was anything but.

Images and tweets of many arrests of demonstrators went viral, including such presumed lowlights as an officer pulling the hair of a handcuffed young black woman and another of the bloodied face of an 84-year-old stopped for jaywalking.

One image showing police after striking a protester brought the remark "Here the #NYPD engages with its community members, changing hearts and minds one baton at a time."

Also largely criticised was the unpopular "stop and frisk" policy, which many argue unfairly targets minority youth.

The NYPD so far has yet to post any happy shots on its Facebook page from its request for public submissions.