With the year’s first quarter nearly in the books, the murder rate in the city has increased by 20.7% compared with the same period last year, a spike chiefly due to an increase in killings in Southern Queens and the Bronx. The number of murders has increased to 17 from eight within Patrol Borough Queens South, a command that patrols neighborhoods such as Jamaica, Ozone Park, and Far Rockaway, a 112.5% jump compared to the same time last year, according to the most recent police statistics. In the Bronx, murders have spiked by 42.8%: There have been 30 homicides recorded this year, compared with 21 during the same period last year.

While elected officials that represent the two areas offered differing theories as to why there has been an increase in homicides, most share similar fears regarding the size of the police department. “New York is the safest it’s been in 40 years,” the president of the Bronx, Adolfo Carrion Jr., said. “These efforts will become increasingly more difficult if we continue to lose veteran police officers to areas outside of New York that offer higher salaries and if our recruiting numbers continue to decrease due to low starting salaries.”

As part of citywide budget cuts, the police department has proposed to shrink its head count by 1,000 officers, a move that would result in the smallest force in 16 years.

The police department’s chief spokesman, Deputy Commissioner Paul Browne, said the increases in killings in Queens South and the Bronx are precisely why the precincts there have been targeted by Operation Impact, a program that saturates high crime areas with officers on foot patrol.

“That’s why Commissioner Kelly directed that all graduates of the last Police Academy class be assigned with experienced supervisors to impact zones there and where other spikes were experienced, and why he directed that the previous cadre of impact officers remain in place — effectively doubling the size of impact,” he said.

The trouble spots in Queens appear to be the 103rd Precinct in Jamaica, where murders have jumped to five this year compared with two last year, and the 101st precinct in Far Rockaway, where four murders have occurred this year compared with one last year. The City Council member who represents Jamaica, Leroy Comrie, a Democrat, said Operation Impact has been very effective, but that a majority of the murders recorded this year have been perpetrated outside of the impact zone, which is in the downtown area of the neighborhood.

Mr. Browne said the police department monitors impact zones and precincts in general, and makes adjustments accordingly. Unlike every other patrol borough in the city, where murders have generally plummeted or at least flat-lined since Mr. Kelly took over as police commissioner in 2002,killings have risen in Queens South. Murders are up 41.6% compared with the same period seven years ago, police statistics show. While the murder rate is up, overall crime has dropped citywide, with major offenses down 0.87% compared with the same period last year.

The president of the Citizens Crime Commission, Richard Aborn, said that with crime continuing to drop, the increase in the murder rate is likely just an aberration.

Mr. Browne pointed out that the citywide increase in homicides so far this year needs to be compared with last year’s record low number.

“The citywide increase so far this year is still the second lowest homicide rate in modern history and 12% lower than two years ago and 36% lower than 2001,” he said.