The chief of staff to Aleksei A. Navalny, the Russian opposition leader who died last month in an Arctic penal colony, was attacked with a hammer and tear gas outside his home in Lithuania’s capital late Tuesday, according to Mr. Navalny’s press secretary, who said the police and an ambulance had been called to the scene.

Leonid Volkov, who served as one of Mr. Navalny’s top organizers, was pulling up to his house in Vilnius when the attack happened. At least one assailant smashed his car window, sprayed him with tear gas and began beating him with a hammer, Mr. Navalny’s press secretary, Kira Yarmysh, said in a statement released on X and in other comments she gave to Russian media.

Mr. Volkov survived the attack.

Photographs posted online by another top aide to Mr. Navalny showed Mr. Volkov conscious but injured, with a mark on his head and blood streaming from one leg. Other photographs showed the bashed-in window of his car, which was parked in a driveway in front of a children’s basketball hoop. Later in the evening, the aide posted a photograph of Mr. Volkov being loaded into an ambulance and taken to the hospital.

“He began to fight back with the car door and with his legs,” Ms. Yarmysh told the exiled Russian news outlet Meduza. “Therefore, they hit him where they could — on his legs.”

The identity of those behind the assault was unknown as of Tuesday night, and it was not immediately clear whether there was one attacker, or more.

The assault on Mr. Volkov happened nearly a month after Mr. Navalny’s death in prison, in circumstances that have not yet been explained.