CINCINNATI (AP)—Police in Cincinnati say three more people suffered gunshot wounds as a violent weekend that saw four killings and at least 20 injuries came to a close.

Police said the three Sunday evening shootings were unrelated, and none of the three victims had life-threatening wounds. Two people were wounded in hands, and a man was shot in the back after a fight broke out at a party, police said.

Those shootings followed four gunfire outbursts early Sunday in which 18 people were shot, four fatally. In one case, 10 people were shot. Police said they are trying to determine why there was such a string of shootings in one weekend. Mayor John Cranley called it “senseless gun violence.”

No suspect information was released immediately in any of the cases.

Police said the department would shift officers from other assignments to increase the number of uniformed officers in the affected communities and would call on federal prosecutors and the Bureau of Alcohol, Tobacco, Firearms and Explosives for help.

Mr. Cranley said the city was facing “unprecedented circumstances and challenges” in fighting crime during the COVID-19 pandemic. He said guns are “far too prevalent” at private gatherings after bars close early under pandemic restrictions.

In July, The Cincinnati Enquirer reported that the city had experienced a rise in shootings and homicides from gun violence during the first half of the year as compared to the same time period in 2019.