NEW YORK (Reuters) – Three quarters of American police officers said their interactions with black people have become more tense following police killings of unarmed black men and waves of protests that followed, according to a survey published on Wednesday.

The Pew Research Center survey found a widespread feeling among police that the general public misunderstood them and the public outcry over the deaths in recent years was motivated by anti-police bias rather than a will to hold police accountable.

Police killings of several unarmed black men in 2014 led to nationwide protests and the rise of the grassroots movement known as Black Lives Matter.

Supporters of the movement, including some Democrats, have said it shines a light on a previously overlooked problem of excessive use of force against blacks by police. Critics, including President-elect Donald Trump and other Republicans, have criticized Black Lives Matter as unfairly maligning police doing a dangerous job.

“Within America’s police and sheriff’s departments, the survey finds that the ramifications of these deadly encounters have been less visible than the public protests, but no less profound,” the researchers wrote in a report accompanying the survey results.

Seventy five percent of officers told Pew their interactions with black people had become more tense in the wake of high-profile police killings of blacks and the protests they generated. Two thirds of officers said the protests were motivated “a great deal” by a general bias towards police.

Two thirds of officers saw the killings of unarmed black men as isolated incidents rather than a sign of a broader problem. This was in marked contrast to the sentiment of the general public, 60 percent of whom said in a separate Pew survey the killings pointed to a broader systemic problem.

More than ninety percent of American police officers said they worried more about their safety because of the protests. About three quarters said they or their colleagues were less willing to stop and question people who seemed suspicious or to use force even when appropriate.

Majorities of police officers and the general public supported the wider use of body cameras worn by officers to record interactions, at 66 percent and 93 percent respectively.

Pew based its findings on online surveys with 7,917 officers from 54 police and sheriff’s departments between May 19 and August 14 last year. There is no single margin of error for the results because of the complex, multi-stage way Pew arrived at its sample of police officers, Pew said.

(Reporting by Jonathan Allen; Editing by Andrew Hay)