Mikhail Kasyanov has been pelted with eggs, the second attack on the Russian opposition figure in recent days.
TASS reported that Kasyanov was targeted as he stepped out of his car on February 11 in the city of Vladimir, some 200 kilometers east of Moscow.
The report said the egg throwers identified themselves as members of the so-called People's Liberation Movement.
Kasyanov, who served as prime minister under President Vladimir Putin and is now a Kremlin critic, was the victim of a similar attack at a restaurant in Moscow on February 9.
Kasyanov said about 10 men of "non-Slavic appearance" had entered the establishment, threatened him, and threw a cake into his face
The Moscow incident came several days after Ramzan Kadyrov, the leader of Chechnya, posted a threatening video on Instagram that shows Kasyanov in the crosshairs of a sniper rifle.
The Kremlin on February 10 called the cake attack an act of "hooliganism" and rebuffed the idea that it was related to Chechnya's leadership.