Kevin Johnson, and Aamer Madhani

USA TODAY

WASHINGTON — Overall violent crime in the U.S. increased by nearly 4% last year, the FBI reported Monday, as several major cities struggled to deal with rising gun violence.

The FBI’s annual crime report found that murder was up 12.8% in cities, driving the overall increase. Property-related crime, however, dropped by 2.6%.

While the one-year violent crime increase was significant, the 2015 total was nearly 1% lower than in 2011 and 16.5% below the level a decade ago, according to FBI records.

FBI Director James Comey, who has previously suggested that violent crime surges in some cities may be a result of a less aggressive law enforcement approach in the face of increased public scrutiny, called Monday for "more transparency and accountability in law enforcement.''

"We also need better, more informed conversations about crime and policing in this country,'' Comey said. "To get there, we are improving the way this nation collects, analyzes and uses crime statistics and data about law enforcement’s use of force.''

As police departments face more questions about the use of deadly force, the Justice Department is seeking to create a database to track deadly encounters between police and the public. A functional repository, however, could take years to establish, officials have said.

The report came just hours before Democratic presidential nominee Hillary Clinton and Republican nominee Donald Trump were set to square off in their first debate of the general election campaign in which crime and the conduct of police have forced the candidates to confront difficult problems in Charlotte, Tulsa and other communities across the country.

In Charlotte, protests have continued since last week's deadly police shooting of Keith Lamont Scott, while Tulsa authorities last week charged a local officer there in the fatal shooting of Terence Crutcher.

Trump, meanwhile, has seized on violent crime spikes in some cities as part of recent proposal to bring back controversial "stop-and-frisk'' tactics in which police have engaged in routine stops of people for searches in part to seize illegal weapons. The practices have drawn the ire of civil rights advocates and some judges who have assailed the tactic as disproportionately targeting minorities.

The FBI's crime numbers, while a measure of last year's criminal activity in the U.S., represent the beginning of troubling developments that continue in cities across the country.

Earlier this year, the Major Cities Chiefs Association, issued its own mid-year violent crime report, which found continuing increases in murder, robbery, aggravated assault and non-fatal shootings, according to data provided by 61 of the nation's largest cities, including Chicago, Las Vegas, Memphis, Philadelphia and San Antonio.

In Chicago, 509 murders have been recorded through Sept. 18, up from 349 during the same time last year--a 46% increase.

Darrel Stephens, executive director of the Major Cities Chiefs Association, said that while the upticks appear to be significant, the numbers may not mean much over time if they are not sustained.

"If this goes on for two or three years, then maybe there is more going on that we need to know about,'' Stephens said.

Other law enforcement analysts also warned against overreacting to the crime numbers, which nationally remain at near 50-year lows. The homicide rate nationally is the sixth lowest recorded since 1966.

“It is not that we are saying the increase is not important, but instead that it takes small numbers to move the rate ten or twelve percent because the crime rate is so low,” said William Lansdowne, a former police chief in San Diego, San Jose and Richmond, California. “We are doing very well.”

Miriam Krinsky, a former federal prosecutor, suggested that reverting to a “tough-on-crime” playbook of the past would prove to be detrimental.

“We know that philosophies around lock ‘em up and throw away the key have failed,” Krinsky said. “We know that mandatory minimums have failed. If we could arrest and jail our way out of the gun violence problem, the neighborhoods in Chicago and elsewhere where there had been an uptick in crime would probably be the safest in America. But that’s not what the facts tells us.”

Acknowledging the violent crime report Monday, Attorney General Loretta Lynch said the numbers are "making clear what each of us already knows: that we still have so much work to do.''

"But the report also reminds us of the progress that we are making,'' Lynch said. "It shows that in many communities, crime has remained stable or even decreased from the historic lows reported in 2014. And it is important to remember that while crime did increase overall last year, 2015 still represented the third-lowest year for violent crime in the past two decades.''

Madhani reported from Chicago