Image copyright Reuters Image caption New York Mayor de Blasio was heckled at the city's police academy graduation

Arrests in New York City are down 66% amid increasing tensions between police unions and the mayor since two officers were shot and killed on duty.

Citations for low-level and traffic offences have dropped by more than 90% compared with the same week a year ago.

The BBC has confirmed the figures, first reported in the New York Post.

On Tuesday, Mayor Bill de Blasio met the city's police unions who have criticised him for what they see as anti-police rhetoric.

Demonstrators in New York City and across the US have focused on what critics say are brutal police actions against unarmed African Americans this year.

Two particular cases highlighted by the protesters were that of Michael Brown and Eric Garner, killed in police encounters in Ferguson, Missouri, and New York City respectively. Grand juries chose not to charge officers in both cases.

The mayor lost police backing when he expressed some sympathy with the protests and said he had to train his mixed-race son in how to deal with police officers.

Unnamed sources told the Post the sharp drop in arrests in the past week was in part because of fears for officer safety but also in part due to a deliberate slowdown.

One union president reportedly told officers to use "extreme discretion" in making arrests, saying "the rules are made by them to hurt you. Well now we'll use those rules to protect us," according to a recording obtained by Capital New York.

A spokesman for the Patrolmen's Benevolent Association denied union leader Pat Lynch was encouraging a slowdown in arrests.

Image copyright Getty Images Image caption Protests supporting police were held in Miami

Image copyright Reuters Image caption Police officers Liu Wenjin (left) and Raphael Ramos were shot while sitting in their patrol car

Meanwhile, an annual report by the National Law Enforcement Officers Memorial Fund found that 50 officers were killed by guns in 2014, a sharp increase from 32 deaths in 2013.

But police deaths by guns remain far below the all-time high of 156 in 1973.

The 2014 figure included 15 ambush deaths, like Officers Rafael Ramos and Wenjian Liu, who were killed last week in New York.

The gunman - who subsequently killed himself - had posted anti-police messages online, referring to Garner and Brown.

The deaths of Ramos and Liu have brought to the fore simmering tensions between police unions representing the rank-and-file officers and the mayor's office.

One union leader suggested Mr de Blasio had "blood on his hands" over the deaths of Liu and Ramos, and some officers turned their backs on de Blasio as spoke at Ramos' funeral.

After Tuesday's meeting, the mayor said the focus of talks were on "building a productive dialogue and identifying ways to move forward together".

Mr Lynch told reporters that officers' safety was his main concern.

"Our thought here tonight is actions speak louder than words and time will tell," he said.