There were two more homicides in Massachusetts in 2016 than the year before,according to data from police departments around the state, with 135 killings last year, up from 133 in 2015. But the number of people killed in Massachusetts last year remains among the lowest number of homicides in at least a dozen years.

Although the number of killings investigated by Boston and State Police rose slightly last year, the number of homicides dropped elsewhere in the state. Overall, the number of homicides statewide has fallen since 2010 when 220 people were killed.

The State Police, which investigates killings in all Massachusetts municipalities except Boston, Worcester, Springfield, and Pittsfield, recorded 67 homicides in 2016, up from 64 in 2015.

But Springfield police investigated 13 killings in 2016, down from 18 in 2015, and Pittsfield police reported three homicidesin 2016, down from four. In Worcester, the number of homicides remained unchanged at eight.

Crime fighting strategies that target gun traffickers and serious offenders, along with prevention and intervention programs designed to keep young people out of the criminal justice system, have led to a steady decline in homicides over the years, Suffolk District Attorney Daniel F. Conley said.

“We know who the individuals are who are driving gun violence,’’ Conley said. “We’re very serious, and there will be serious consequences.’’

Last year, law enforcement agencies targeted large drug enterprises in Lawrence and dismantled violent gangs such as MS-13. Federal, state, and local police charged 56 members of the international street gang, which officials said was responsible for five murders throughout Greater Boston.

“Large-scale targeting of multiple offenders does help get potential offenders of violent crime off the street,’’ State Police spokesman David Procopio said. “It sets the tone that preserves a sense of law and order.’’

The State Police also ­focused on major heroin traffickers, who also tend to be a magnet for street violence and crime, Procopio said.

Experts attribute the slight increase in killings in 2016 to gang feuds, which can fluctuate year to year.

“Gang homicides tend to move upward and downward,’’ said James Alan Fox, a criminology professor at Northeastern University.

State Police said they cleared, or solved, 87 percent of homicides investigated by the department last year, which included fatal street shootings, domestic violence killings, and murder-suicides in urban and suburban areas, Procopio said. A case is considered cleared when an arrest is made or when a suspect is identified but ­deceased. Springfield police solved seven homicides. ­Pittsfield police solved one, and Worcester ­police solved three.

In Boston, where the number of homicides increased by five in 2016, Commissioner William B. Evans said officers focused on getting the most violent criminals off the street and seized 777 guns last year.

Molly Baldwin, founder and executive director of ­ROCA, an organization for at-risk youth, said far too many firearms remain on the streets.

“It’s something we always have to work at,’’ she said. “The more we work together, the better chance we have to help those who have gone astray, change lives, and help young people who are at risk.’’

Middlesex District Attorney Marian T. Ryan said law ­enforcement officials statewide worked with local school officials and community groups to provide prevention services to people “who are on a cyclical, predictable pattern of self-destruction.’’

Ryan, president of the Massachusetts District Attorneys Association, said cities in ­Massachusetts are seeing now the results of what has been the last eight to 10 years of work.

However, she said the state could improve services and ­expand resources to people ­recently released from prison to reduce recidivism rates.

Law enforcement officials said that they hope the number of homicides will continue to decrease, but that it requires a collaborative effort.

“Some may say it’s all the ­police, but all of us lend to the local success,’’ Chelsea Police Chief Brian Kyes said. “It’s all about partnerships and ­joining forces.’’

Jan Ransom can be reached at jan.ransom@globe.com. Follow her on Twitter at @Jan_Ransom. Todd Wallack can be reached at twallack@globe.com. Follow him on Twitter @TWallack.