Violent crime in Suffolk County dropped by 13 percent in the first 11 months of 2013 and homicides rose to 27 last year, up from 23 in 2012, according to police records.
Suffolk's year-end violent crime statistics -- including December -- have not been completed, police said.
In Nassau, violent crime fell by 15 percent last year and homicides dipped to 25 in 2013 from 27 in 2012, according to police data through Nov. 30, the most recent statistics available. In both counties, violent crime includes such offenses as murder, rape, assault and robbery.
A total of 29 people were killed in Suffolk in 2013, but police officials said two of those deaths do not count toward the homicide total because one was charged as an assault -- rather than murder or manslaughter -- and the other is still being investigated by the medical examiner's office.
"While the number of homicides in Suffolk County continues to be below the five- and ten- year average, every homicide is unacceptable," said William Madigan, chief of detectives for Suffolk County police. "We will be strengthening a number of initiatives to address this issue as we continue to drive down overall crime."
Suffolk and Nassau counties have some of the lowest rates of homicide and violent crime in the country when compared with areas with similar populations, state and federal records show.
In a statement responding to the latest homicide statistics, Nassau County Executive Edward Mangano said the county "leads the nation in safety."
In Suffolk, however, the increase in homicides bucked a national trend of homicides decreasing in large population centers.
In New York City, for example, homicides plunged to 333 last year -- a 20 percent decrease from 2012 and the fewest in the five boroughs since modern record-keeping began in the 1960s.
Just a handful of large counties, including Baltimore County in Maryland, saw an increase in homicides.
In response to the increase in Suffolk, police said they would strengthen programs aimed at preventing murders and other violent crimes, including a new anti-drug initiative, the details of which the department said it could not release for strategic reasons.
Experts said the annual increase in Suffolk is not significant.
"Statistically, it's a bleep," said Eli Silverman, professor emeritus at John Jay College of Criminal Justice in Manhattan. "That number alone doesn't suggest to me that the police are any less vigilant."
Gun violence, too, increased in Suffolk last year, records show, a rise police blame largely on drugs and gangs. They say those causes are also behind the increase in homicides.
Sixty-three people were wounded by gunfire in areas patrolled by the Suffolk County Police Department between Jan. 1 and Nov. 30, according to records compiled by the department. That represents a 21 percent increase from the same period last year, when 52 people were shot.
Concerns over gun violence have also carried over into the new year.
In Deer Park, two people opened fire on a Cadillac in a park early Thursday, killing one man in the vehicle and seriously wounding another in a possible gang shooting, police said.
Two days earlier, a volunteer with South Country Ambulance was struck by debris when someone fired a bullet or high-powered pellet through the rear window of an ambulance in Bellport. The ambulance crew members were wearing bulletproof vests as the result of a policy instituted about 18 months ago following a rise in gun violence in the area, an EMS official said.
The uptick in Suffolk killings and shootings followed a banner year for the department in 2012. Homicides that year fell to 23, a 10-year low for the county and a dramatic decrease from 2010, when detectives investigated 52 killings, records show.
The department's homicide total in 2012 was the lowest since 2002, when it reported 18 killings.
"When you look at all the numbers, we're one of the safest communities to live in," Madigan said. In Nassau County, homicides rose from 23 in 2011 to 27 in 2012.
Gun violence continued a downward trend there in 2013, with 29 people wounded by gunfire in the county police department's jurisdiction between Jan. 1 and Oct. 31, the most recent records show. In 2012, 38 people were wounded by gunfire.
As for solving homicides, Suffolk police said they have closed 15 of the 27 homicide cases recorded in 2013 -- a 55.5 percent clearance rate. Homicide cases are considered cleared once police identify the suspected offender.
In Nassau, detectives cleared 19 of their 25 cases in 2013, for a 76 percent clearance rate, according to department records.
The national average for clearance rates, last calculated by the FBI in 2011, was 64.8 percent.