The NYPD's chief of department said Monday police are "struggling" to keep up with a recent increase in homicides and shootings at a time when overall serious crimes continued to drop.

James O'Neill said the NYPD will reassign 330 cops from desk jobs to walking the beat by next Monday in an effort to contain a 19.5 percent increase in killings and almost 9 percent rise in shootings over last year -- a trend some cops fear could escalate further with the warmer weather.

"We are struggling with homicides and shootings," O'Neill said. "We are doing everything in our power to knock that down."

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The redeployment, known as "Summer All-Out," began last year in July but is being rolled out a month early this year to deal with escalating street violence, he said.

There were 135 homicides and 439 shootings from January to May this year, compared with 113 homicides and 403 shootings in the same period last year, according to the latest statistics provided by the department.

However, serious felonies were down 6.6 percent from last year -- the lowest since 1994, he said.

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Shootings and homicides historically increase in the summer months, O'Neill said.

Twenty-three more shootings occurred in the 28 days ending Sunday over the same period last year, but the increase in homicides was only fractional during that time, O'Neill said.

Police believe gang activity is a significant factor in the increase in violence, which is believed to be committed by suspects with previous arrest histories.

Firearms were used in more than 80 percent of the 31 homicides that occurred last month -- a marked increase from the more typical 56 percent, said Dermot Shea, deputy commissioner of operations. Six of those killings were believed to be gang-related, Shea said.

The May 22 killing of 14-year-old Christopher Duran as he walked to school in the Bronx was an outgrowth of a gang dispute involving one of Duran's relatives, chief of detectives Robert Boyce said Monday. Two men are being sought by police for that shooting.

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Some cops have said privately they believe a massive drop in stop and frisk activity has emboldened criminals to carry guns.

The NYPD performed 7,125 stops through March 31 this year, compared with 14,261 in the same period in 2014.

O'Neill said if the department sees an increase of violence in a certain area, "we are going to put more resources in there -- but the stops we want are good stops."