Serious crime in the city of Manassas climbed last year, primarily due to two types of offenses that spiked during 2012, according to the city’s recently released annual report.

Manassas also implemented two new tactics to combat crime in the past year, combined with its ongoing efforts to put an emphasis on community policing, police Chief Douglas W. Keen said in an interview. A crime analyst helped police target “hot spots” around the city and a new Special Problems Unit helped target areas and assured that police were being proactive to prevent crime, he said.

That’s part of the reason that crime went down in many areas, Keen said. Aggravated assaults, however, jumped from 46 to 54, an increase of 17 percent from the year before. Larceny, or theft without the threat of force, jumped from 680 the year before to 786, or 14 percent. Many of those crimes are thefts from vehicles, officials said. Those two offenses were responsible for the serious crime increase of 8 percent overall in 2012.

Graffiti and domestic violence charges — including rape — were down last year, the report said. Murders in the city dropped from four to three, and forcible rapes went from 22 to 15, a 32 percent drop, according to the report.

“It’s showing that we’re out there [preventing crime],” Keen said.

The Special Problems Unit consists of five officers and a supervisor that operate on flexible schedules so they can work when needed, Keen said. They have helped on assignments throughout the year, he said, including to try and track down who is leaving crudely written, threatening notes in the Sumner Lake neighborhood.

The perpetrator has not been caught, Keen said. The unit has also helped with narcotics arrests and traffic enforcement. “They do a lot of work they might not actually get the credit for,” Keen said.

The report showed that the Georgetown South and Point of Woods neighborhoods — Manassas’s densest areas — had the greatest concentrations of crime.

Meg Carroll, community manager of Georgetown South and a former Manassas police officer, said that while the relationship between her community and police has improved, it is sometimes strained.

“I still wish we had an active partnership with them,” Carroll said. She said that because the community is mostly Hispanic, she’d like to see more Hispanic officers assigned to Georgetown South. Many in the community are “scared of the police,” she said, and want to see a police force “as diverse as they are.”

Manassas has 11 Hispanic officers out of 129, according to department statistics. Keen said that it has been a struggle for every Northern Virginia law enforcement agency to recruit a diverse force. Manassas’s police force, however, is nearly 25 percent women — one of the best in the region in that area, Keen said.

“We’re out there recruiting,” he said. “Every one of us [in the region] ... would like to have more diversity.” He also said that he is competing for the same small pool of diverse applicants with other law enforcement agencies, who sometimes can offer better salaries and benefits.