Washington (AFP) - White police officers are more likely to use their firearms than their black colleagues, and even more so in majority-black neighborhoods, according to a study.

The study, published Monday, reinforces a sentiment often expressed by minority communities in the US.

When called on emergency response operations, white officers "use gun force twice as often" on average as their non-white colleagues, wrote Mark Hoekstra and CarlyWill Sloan, economists from Texas A&M University.

Additionally, "while white and black officers use gun force at similar rates in white and racially mixed neighborhoods, white officers are five times as likely to use gun force in predominantly black neighborhoods," they said in the study, which was submitted for discussion on the National Bureau of Economic Research website.

In order to calculate their results, the researchers combed through more than two million calls to the 911 emergency line in two major US cities -- which were not specified -- that dispatch officers randomly.

The sample therefore does not necessarily represent the whole country, but it is large enough to demonstrate that "race matters even in a time and context during which police departments generally, and white officers in particular, know they are under close scrutiny by the media and the public," Hoekstra and Sloan wrote.

They noted that 24 percent of black US citizens express very little confidence in local police forces.

Black civilian deaths due to white police brutality regularly cause an uproar in the US, where they have given rise to the "Black Lives Matter" movement.