Serious crime on Metro was down about 5 percent last year overall, but aggravated assaults, rapes and other violent crimes increased by significant proportions, according to statistics released Monday, likely fueling a perception that the transit system has become more dangerous.

Aggravated assaults were up 31 percent last year to 151, and represented the most dramatic increase in crime in the system. The attacks largely involved men between 18 and 24, who were most often both the victims and suspects in such attacks, according to the statistics. An aggravated assault occurs when a person uses a weapon or flashes one in a threatening way, or when a person is severely injured in an scuffle.

Homicides and rape, the most serious offenses — but also infrequent — also increased, with five of each logged in 2016. In 2015, there were two homicides and no rapes reported, according to statistics.

Last year was marked by several high-profile incidents that raised fears among many riders and led to calls for an increased police presence on trains and in stations. A 16-year-old boy was arrested in February in connection with the shooting of a man on a Green Line train, the only instance officials could remember for more than a decade in which a person had opened fire on board a train. In March, a 15-year-old boy was fatally shot on the platform at Deanwood as he was on his way to get a haircut for Easter.

Two weeks later, a 15-year-old boy was fatally stabbed at the station’s fare gates in a dispute with an 18-year-old man. That same week, a woman reported being raped on a moving Red Line train in the Wheaton-Glenmont area of Montgomery County. Metro did not publicize the incident, however, and it came to light more than a month later in court.

Asked about the perception that the system is more dangerous, Metro Transit Police Chief Ron Pavlik Jr. conceded, “Some of it is violent crime is up. The numbers are reflecting that.”

“It’s that victim who decides ‘you’re not going to get my phone today. Now a theft-snatch it turns into a tussle, a physical altercation has ensued,” Pavlik said. “Some of it is just escalation of crimes.”

For example, although robbery was down overall, armed robberies increased from 110 to 117.

Still, Transit Police touted progress in other areas: Bike thefts and assaults on bus operators are down, and they’re nabbing fare evaders more frequently. In July, officers were outfitted with uniforms designed to make them more visible in stations. The agency also made use of a new $3.6 million surveillance hub in Hyattsville, Md., where authorities can monitor violent incidents as they happen, and dispatchers can log complaints and text tips to officers in the field.

Crime experts say the uptick in violent incidents matches trends observed in cities where some lower-level offenses have decreased but violent crimes have been on the upswing. The Major Cities Chiefs Association, an organization of police chiefs in the country’s largest cities, published reports last year showing that violent crime has been increasing in large cities nationwide.

“Aggravated assault was the crime that increased the most [on Metro]” said Darrel Stephens, executive director of the Major Cities Chiefs Association, referring to the hard statistics. “That is consistent with reports from some of the cities when talking about violent crime increases.”

Assaults on bus operators decreased 14 percent, dropping to 75 incidents last year, partly because of increased surveillance, Pavlik said. Metro installed video monitors on X2 buses in late 2015 after a spate of assaults on operators on that line. Pavlik said Metro has had success with video surveillance.

“The biggest thing we’re really trying to push — I’m trying to push in 2017 — is more real-time intelligence sharing: ‘How can we better communicate with officers in the field?’ ‘How do we use technology to better facilitate intelligence?’ ” Pavlik said.

But David Stephen, a spokesman for Amalgamated Transit Union Local 689, which represents a majority of Metro’s 13,000 workers, said assaults on operators continue to be a concern for the union.

He pointed to a November incident in which a woman allegedly threw hot soup on a bus operator following a fare dispute, and the driver had to be treated at a hospital. The union blamed plexiglass shields installed in buses to protect drivers, which it said have a “poor design and open gaps” that left the operator vulnerable.

“It’s great that the numbers are down . . . but there’s still some work to be done when it comes to collaboration on how to address the potential for assault,” Stephen said. “That was a telltale sign that there are some gaps in safety that need to be addressed and that can only be achieved through collaboration.”

Stephen said the discussion will become more important only as Metro weighs fare hikes in the coming year. Metro says fares are the primary driver of disputes on board buses.

Transit Police were responsible for only one of the homicide investigations, after one of the agency’s officers chased a suspect outside the Addison Road Metro station. A Fairfax County man was charged with fatally stabbing a 35-year-old man after an argument at a bus bay just outside the station entrance. The other four investigations were headed by local authorities. The homicide statistics include separate killings that happened two weeks apart at Deanwood — the one on the train platform in March and the stabbing at the fare gate.

“Some of that is neighborhood beef that might have spilled over to Metro,” Pavlik said. “Metro is not immune to the crime that happens in the neighborhoods that surround it.”

After the reported rape of the woman on the Red Line train — which happened during day — there was a public outcry that Metro had not publicized the incident or circulated information about the suspect.

Metro acknowledged that its response was wrong and instituted a policy to report violent crimes the same day they happen.

Two of the rape cases were determined to be “unfounded,” meaning there was no evidence that a crime had occurred. Metro said a suspect was identified in each of the others.

The statistics include only Category 1 offenses — serious crimes logged in an FBI database. They do not, for example, include instances of indecent exposure — despite their prevalence in the system. A May incident in which a suspect allegedly put a “fluid-filled” condom on a woman’s shoulder aboard a Blue Line train was classified as a simple assault and also was not included.

Meanwhile, bike thefts fell by 15 percent, and officers issued 40 percent more citations for fare evading last year compared with 2015. It was a dramatic increase — 6,693 citations in 2016 compared with 4,751 a year earlier. Officials said the citations resulted from increased enforcement, including a program known as “High Intensity Target Enforcement”, in which officers swarm an intersection and meet with bus operators passing through, board buses and issue citations.

The “primary driver is safety, but ensuring that every rider pays the proper fare is a stated goal of the GM,” Metro spokesman Dan Stessel said.