About 200 demonstrators from each group stood outside the mosque in Phoenix, Arizona, where a biker crew had said they would hold a blasphemous cartoon contest.
Dozens of officers lined up between the two sets of protesters, using yellow police tape to separate them near the gates of the Islamic Community Center mosque in north Phoenix.
The anti-Islam protesters held placards and had a shouting match with rival demonstrators across the police lines.
Several of the protesters were heavily armed — some with AR-15 assault rifles — and wore military fatigues. Arizona has some of the laxest gun laws in the United States.
But after several hours of tension, the standoff eased — though officers kept the two groups apart.
Organizers of the protests said on their Facebook page that it was in response to an attack in Texas where two gunmen were shot dead before they could storm a blasphemous cartoon competition. – AFP