DALLAS – As many as four police officers were killed while six others were injured when unidentified snipers opened fire at police during “Black Lives Matter” protests in the downtown area of Dallas after police shot dead two black men in questionable circumstances.

According to media reports, three suspects were detained immediately after the incident, while an intense search operation has also been initiated in the area.

Dallas Police Chief David Brown, in a statement released to media, confirmed the firing incident saying “two snipers have shot 10 officers, four of whom were killed while two officers were in surgery.”

Some media reports also claimed that the two snipers who apparently killed the police officials were also shot dead minutes after the firing.

Last week, a 37-year-old African-American man identified as Alton Sterling, was pinned to the ground and then fatally shot in the chest outside a store in Louisiana. The officers claim they were responding to a call about a black men threatening passersby with a gun.

In a separate incident on Wednesday, another African-American man named Philando Castile was shot and killed by a police officer during a traffic stop near Minneapolis, Minnesota.

The deaths of Sterling and Castile are the latest in a series of incidents from Baltimore, Chicago, New York and Cleveland where the police has allegedly used unprovoked lethal force on African-American men, spurring many observers to allege racial bias in their operations.