A man who apparently was distraught after an argument with his wife blew himself up near a Moscow supermarket, killing himself, ITAR-Tass news agency reported.
No other injuries were reported in the incident in the city's northeast.
The wife of the man told police that her husband had quarreled with her about three hours earlier, after which he grabbed a gun and left their home, police spokesman Anatoly Lastovetsky was quoted as saying by ITAR-Tass.
Lastovetsky did not specify how the man blew himself up, but the Interfax news agency reported that witnesses said he parked his automobile near the supermarket, went to its entrance while muttering unintelligibly, pulled out a grenade and set it off.
There were no indications the act was intended as terrorism and ITAR-Tass cited the spokesman as saying the domestic quarrel was apparently the motivation.
But the explosion initially sparked fears that it could be a terror attack in a city that experienced one just over a month ago. A suicide bomber killed 37 people in a Jan. 24 blast at Moscow's Domodedovo airport, the country's busiest. A leader of Islamist insurgents in Russia's Caucasus claimed responsibility for ordering that attack.