Moscow rocked by apparent suicide bombing

The outlet noted that, according to officials, the explosion also left two other officers injured.

The AP also reported that Russia's top investigative agency said the assailant was a 22-year-old man from Russia's Udmurt Republic and that there was an ongoing probe regarding the motive behind the attack.

Russian President Vladimir Putin allegedly said at a meeting with top officials from Russia's Federal Security Service (FSB) that the young man was recruited online and was unknowingly given an explosive device that was then detonated remotely, according to the AP.

The Associated Press contributed to this report.