MOSCOW — The investigation into the killing of Boris Nemtsov, a fierce critic of Russian President Vladimir Putin who was gunned down not far from the Kremlin, faced conflicting reports today about possible surveillance footage of his slaying.

No suspects have been arrested since Nemtsov was shot dead Friday night on a Moscow bridge, a slaying that came just hours after a radio interview in which he denounced Putin’s “mad, aggressive policy” in Ukraine. According to Russian investigators, Nemtsov was walking near the Kremlin on his way home with a woman when he was shot four times by an assailant, who then escaped in a light-colored car.

It was not clear what CCTV footage may have captured his slaying, even though the area is one of the most highly secure parts of the Russian capital.

The business daily newspaper Kommersant quoted anonymous sources in the Interior Ministry as saying there was no CCTV footage of his killing because the cameras in question were not working at the time.