Arrests and summons activity by NYPD officers, although still down, has bounced back in the past week, Police Commissioner Bill Bratton said Monday.

The increase, coming after concerns that cops in recent weeks were turning their backs on crime, was still down substantially from a year ago, Bratton said.

"We are still concerned with the levels of activity but they are returning to normal with each passing day, each passing week. Those numbers are going back to what we describe as normal levels," Bratton told reporters during a briefing at police headquarters.

Bratton also released the latest crime statistics that noted serious crimes in the city, including homicide, continued to decrease even with the slowdown.

Every borough and precinct has experienced a crime drop in 2015, Bratton said, adding that the decline fit in with the city's historic falling crime rate trend over the past two decades. For the year to date serious crimes were down nearly 11 percent from 2014, with killings down 20 percent, he said.

Surrounded by key members of his executive staff and major commanders, Bratton chalked up some of the slowdown to the funerals for officers Wenjian Liu and Rafael Ramos. The officers were shot and killed Dec. 20 as they sat in their police vehicle in the Brooklyn by a gunman who had posted anti-police messages on social media.

Bratton said the doubling up of highway and traffic enforcement patrols, as well as coverage of demonstrations after a grand jury declined to indict an NYPD officer in the apparent chokehold death of Eric Garner, also contributed to the slowdown. Some union officials and law enforcement experts believed anger and dissatisfaction with Mayor Bill de Blasio contributed to cops ignoring quality-of-life offenses.

For the week ending Jan. 11, police made 4,690 arrests of all kinds, down 37.5 percent from the same period in 2014 but an increase of over 95 percent from the previous week when the slowdown appeared to be at its peak, police data showed.

The increase in police activity was more dramatic in the area of summonses, which increased by 540 percent last week for parking and moving violations as well as criminal offenses, the data showed. Last week cops wrote a total of 12,365 summonses, which, although down on average by about 70 percent from the same period in 2014, was a large jump from 2,287 recorded in the week ending Jan. 4. At one point summonses had dropped by on average 90 percent from a year ago, according to NYPD statistics.

Bratton noted the summons numbers were expected to increase for each week because of a time lag in inputting the data from the paper documents.

"You wouldn't expect it to come back in one week," police historian and author Thomas Reppetto said of policing activity. "It may not go back to what it was in 2014, but it will be a respectable number."

"A slowdown is a losing issue for everyone," Reppetto said.

Fiscal experts have reported that the city lost an estimated tens of millions of dollars in potential revenue from the decrease in summonses.