Police Officer Juan Diaz. (Photo: Agencies)

LOS ANGELES, Aug. 2 (Xinhua) -- Los Angeles police conducted raids in two counties on Friday morning and arrested three primary suspects days after the fatal shooting of an off-duty Los Angeles Police Department (LAPD) officer last weekend, authorities said on Friday.

Los Angeles Mayor Eric Garcetti and LAPD Assistant Chief Beatrice Girmala confirmed the arrests in brief remarks before a graduation ceremony at the Police Academy in Elysian Park, according to local media reports.

LAPD officer Juan Jose Diaz was shot dead last Saturday at a Lincoln Heights taco stand, northeast of downtown Los Angeles.

The suspects in custody were only identified as being in their 20s.

Garcetti described the shooting of the 24-year-old off-duty officer as a "senseless murder," adding that the arrests were the result of more than 100 officers and detectives working round-the-clock shifts.

The mayor noted that Diaz had expressed an interest in becoming a policeman while growing up in Northeast L.A., went on to do "exceptionally well" at the academy and "was doing what a police officer does -- protecting his community" when he was gunned down.