Unidentified attackers beat up an activist campaigning for hospitalized Russian opposition leader Alexei Navalny in the Urals city of Chelyabinsk, his colleagues said Thursday.

Alexei Baraboshkin, the local coordinator for Navalny, was “assaulted by unknown attackers” late Wednesday after receiving threats for several weeks, his campaign office wrote on Telegram.

It posted a picture of him with a bruised and bleeding eye.

Navalny is being treated in Germany for poisoning with Novichok in an incident that has sparked international condemnation and the threat of sanctions against Russia.

The Kremlin critic was leading a nationwide tactical voting campaign aimed at pushing out the ruling party in polls this weekend for regional and local assemblies.

Doctors suspected the Chelyabinsk campaigner suffered a fractured skull and concussion, according to a medical document posted by his team, who said the attackers did not take his money or phone.

A police spokeswoman in Chelyabinsk said officers were carrying out a check after receiving a report from the hospital, the RIA Novosti state news agency reported.

Chelyabinsk residents on Sunday will vote for regional and municipal deputies.

Early voting will begin nationwide from Friday, in a move to reduce the coronavirus risk at polling stations, while opposition activists fear this will make it easier to falsify the results.

Regional campaigners for Navalny have reported numerous threats and acts of intimidation as well as regular searches of their homes and detentions by police.