(Reuters) - Police in New Haven, Connecticut, on Friday pleaded for an end to a spate of battles with paintball and BB guns on city streets in broad daylight, warning they had received more than a dozen 911 calls from residents who believed the weapons were real.

While the guns involved were not lethal, police said they were difficult for residents to differentiate from actual firearms, noting that one woman made a frantic call to report two gangs battling with assault rifles on her street.

"We're trying to avert a tragedy," said Assistant Chief Achilles Generoso in a statement on Friday. "The effort to stop this is a top priority for our department."

The United States has been rocked over the past two years by a long series of police shootings of unarmed black men and boys, some of which involved toy guns or items that police mistakenly believed were guns.

Police in Cleveland, Ohio, in November 2014 shot dead 12-year-old Tamir Rice after a 911 caller reported a man with a gun in a park. Rice was holding a toy gun.

New Haven police have been confronted by angry crowds at least once when they responded to reports of armed teenagers only to find that the weapons in question were not real firearms, the department said.

They also noted that a 10-year-girl was injured when a person with a BB gun shot her in the head. Police said they are looking for the people who carried out that shooting.

"This has got to stop before someone is seriously hurt or worse," said Karl Jacobson, supervisor of the department's intelligence division.

(Reporting by Scott Malone in Boston; Editing by Matthew Lewis)