Chicago marked its 500th homicide of the year over the U.S. Labor Day holiday weekend, after 13 people were shot dead in an ongoing spike in violent deaths, the Chicago Tribune reported Tuesday.

A surge of killings occurred between the early hours of Monday and Tuesday in what police believe was a spate of retaliatory violence mainly involving gangs to avenge affronts from earlier in the weekend, the newspaper reported.

A total of 65 people were shot over the Labor Day weekend, with nearly half of them in the last of the three days.

According to the Tribune, the city's homicide count now stands at 512 for 2016.

The Chicago Police Department put the number at 488 as of late Monday, an officer in media relations told AFP on Tuesday.

The Tribune said its figure was higher because it includes highway killings and homicides which are considered justifiable, unlike the police tally.

A retired pastor who was heard arguing with another individual was shot in the face and died near a senior housing complex, the paper reported.

The uptick in violent deaths has brought Chicago's murder rate in line with levels not seen since the 1990s, when more than 900 people were killed annually, the Tribune said.

The deadly holiday shootings far outpaced Chicago's other summer three-day weekends: six people died in shootings over Memorial Day in May and five over Independence Day in July.

New York, in contrast, experienced its safest summer in more than 20 years according to crime statistics unveiled Tuesday by outgoing police commissioner Bill Bratton. The city has long proclaimed itself the safest big city in the United States.

Overall reported crime was down five percent in the three months from June-August compared to the same period in 2015, and down 73 percent since 1994 when Compstat records began.

In August, murders were down 2.9 percent, rape down 6.7 percent and robbery down 15 percent compared to the same month in 2015.

For context, New York recorded 1,946 murders in 1993 and 352 in 2015.