A series of unusual violent crimes in Cambridge over the past weeks has left community leaders concerned for residents’ safety, with some calling for an increased police presence in their neighborhoods.

A fatal street stabbing in the last days of May, three shootings in five days early in June followed by a reported double rape at the end of the month constitute a surprising rise in violent crime in a city that averaged two murders per year over the course of the last decade.

Cambridge Police Department spokesperson Frank Pasquarello discounted suggestions that the city was experiencing a crime wave.

“Cambridge is a very safe place to live and work. It’s just unfortunate that we’ve had three shootings within five or six days,” he said.

None of the victims of the recent shootings were randomly targeted, Pasquarello noted.

“It’s believed that these were not random acts of violence...in every case, the suspects knew the person they were shooting at.”

But in Riverside, the neighborhood where recent violence has been concentrated, some residents are convinced that the crimes reflect larger trends of rising violence and reveal a need for heavier law enforcement.

“I think it’s disgraceful. It’s a very sad time for us,” said Riverside resident Joan Qualls-Harris. “I think this sort of thing is happening across the country, and I’m afraid that it’s something that’s not going to stop if we don’t have police and community connected to address the issue.”

Residents say a decrease in the number of officers—due to retirements, according to city officials—is leaving neighborhoods under-policed.

Harris said she thinks that the key to mitigating crime rests with the police’s expertise.

“I think we need more and very serious police protection in the community, because I think these kinds of activities are happening among people the police are familiar with,” she said.

Members of the community scheduled two meetings last month to address the recent surge of crime, according to Riverside resident Alec Wysoker ’84.

Though no decision on an appropriate response has yet been reached, Wysoker said, several residents issued a call for more community policing.

According to Mayor Michael A. Sullivan, his office has been working closely with the police commissioner to enhance law enforcement resources. The Cambridge Police Department recently sent a group of newly hired recruits to the state police academy and expects them to join the force by the end of the summer.

The city is also reevaluating its approach to policing, Sullivan said. Currently, a pilot program aimed at establishing an effective community-based policing system is underway in the Area 4 neighborhood, which abuts the Riverside district.