An intruder smashed a bottle containing a chemical fluid in the campaign office of allies of Kremlin critic Alexei Navalny in the Russian city of Novosibirsk on Tuesday, forcing them to evacuate the premises, opposition activists said.
Two people were treated by medics and at least one was taken to hospital, said Sergei Boyko, an opposition politician and ally of Navalny, who is being treated in hospital in Germany after what Berlin said was an attempt to kill him by poisoning.
Boyko, who is running for the city council of Novosibirsk in Siberia in an election on Sunday, said it was unclear what substance had been thrown in the campaign office but that police had said it was not toxic.
Boyko's election campaign group described it as a chemical that was caustic and foul-smelling.
CCTV footage shared by Navalny's allies showed two hooded men sprinting away after the incident. The activists had gathered to listen to a talk on how to monitor elections, Boyko said.
Boyko is one of a number of supporters of Navalny running in local elections across Russia at the weekend.
Navalny was admitted to hospital last month after collapsing on a plane to Moscow from Siberia, where he had met with allies running in the elections.
He was airlifted to Germany for treatment and Berlin has since said he was poisoned with a Novichok nerve agent. Russia has said it has seen no evidence that he was poisoned.