Chicago police reported 51 homicides in the city during the first month of 2016, the bloodiest figure for the month in the past 16 years.
The city's homicide total compared with 29 in January 2015 and 20 in January 2014.
Also, the number of shootings more than doubled in January to 242, compared with 119 such incidents in January 2015. The number of shooting victims more than doubled as well, to 292 from 136.
In 2012, Chicago had more than 500 homicides, the highest of any U.S. city.
The Chicago Sun-Times reported that the city's street cops blamed the rise on the police department's agreement with the American Civil Liberties Union to closely scrutinize police stops.
"Cops say they have avoided making many of the stops they would have routinely done last year," the newspaper reported. "They fear getting in trouble for stops later deemed to be illegal and say the new cards take too much time to complete."
The newspaper said that beginning in January, officers have been required to fill out two-page forms "documenting every stop of a citizen for everything from traffic violations to investigative stops."
Chicago police have come under scrutiny for several highly publicized shootings, including December's shooting of Quintonio LeGrier, a young man whose father described him as "mentally disturbed," and the 2014 shooting of black teen Laquan McDonald, who was shot 16 times.
Video showing a white officer shooting McDonald sparked protests and launched a federal civil rights investigation of the police department.