Mayor Bill de Blasio and Police Commissioner Bill Bratton at a Nov. 10, 2014 press conference where it was announced that most people caught with 25 grams or fewer of marijuana would be issued a summons instead of getting arrested. View Full Caption DNAinfo/Ben Fractenberg

NEW YORK CITY — Murders are up 20 percent since last year and the NYPD says pot dealers are to blame.

Police said Monday there have been a spike in drug-related murders and drug-related shootings account for 15 percent of all shootings, though they couldn't immediately provide numbers on either.

Robert Boyce, the NYPD Chief of Detectives, said that most of the drug-related deaths are robberies.

“These are all ripoffs. These are not turf battles,” he said at a press conference. “These are ripoffs of marijuana dealers, robberies. That’s where we’re coming from.”

There have been 54 homicides so far this year, compared with 45 during the same period in 2014. Shootings were also up to 151, a nearly 20 percent spike from last year.

Police Commissioner Bill Bratton blamed illicit marijuana sales and said the problem today was worse than the 1990s when the city's murder tally ballooned to 2,245, averaging about 187 deaths a month.

“The seemingly innocent drug that’s being legalized around the country — in this city, people are killing each other over marijuana,” he said.

NYPD Deputy Commisioner of Operations Dermot Shea said marijuana often comes up when homicide arrests are made.

"When you dig down into that criminal arrest history of the individuals arrested for homicide this year, we see controlled substance and we see marijuana," Shea said. "But we're seeing marijuana at a 2-1 percentage over the controlled substance. Marijuana is coming up repeatedly."

Still, advocates who are pushing for more progressive marijuana legislation argued that the numbers vindicated their cause as well.

“This is a perfect illustration for why marijuana should be regulated and controlled by the government,” Rachelle Yeung, a legislative analyst at the Marijuana Policy Project said. “If there has been an increase in [violence] it’s because the government is leaving the current marijuana market in the hands of criminals.”