The FBI released crime data Monday morning showing that murders in the United States rose by 10.8 percent last year.
The sharp increase is the greatest single-year percentage jump since 1971 and follows a more than two decade trend of falling crime rates, the Wall Street Journal reported.
Violent crime increased 3.9 percent in 2015 while property crimes dropped 2.6 percent, compared with 2014, according to the FBI. The rise in murders was significantly prominent in Chicago, Baltimore, and St. Louis.
FBI Director James Comey called for "more transparency and accountability in law enforcement" upon releasing the figures. He also urged "better, more informed conversations" regarding crime and policing in the U.S.
Comey has suggested that the so-called "Ferguson effect" is causing spikes in violence across the country due to the hesitance of police officers to do their jobs because they are worried about having their actions filmed or publicly scrutinized.
He said in May the effect, named after the 2014 protests in Ferguson, Missouri over the shooting of Michael Brown, could be related to "marginal pullbacks by lots and lots of police officers.
The Obama administration has adamantly rejected the link between increasing murders and protests over police violence.
Attorney General Loretta Lynch said in a speech Monday the FBI report shows "we still have so much work to do."
"But the report also reminds us of the progress that we are making. It shows that in many communities, crime has remained stable or even decreased from historic lows reported in 2014," Lynch said.