Russian police have forced their way into the Moscow office of opposition leader Alexei Navalny, according to a spokeswoman for the politician.
Images broadcast online by supporters of Mr Navalny showed officers arriving at the building on Sunday morning and beginning to question people, with spokeswoman Kira Yarmysh claiming they used an angle grinder to gain entry.
Ms Yarmysh said she thought the raid was designed to shut down the work of Mr Navalny’s TV studio, which broadcasts bulletins and other videos on YouTube.
The incident comes as hundreds of backers of the 41-year-old begin a nationwide day of protests against the authorities, calling on voters to boycott what they believe will be a rigged presidential election on 18 March.
Last month Mr Navalny was barred from running in the election by Russia’s central election commission because of a suspended prison sentence for fraud, but thousands still turned out to endorse him for the presidency during demonstrations across the country.
In a video message addressing his supporters following the commission’s decision, Mr Navalny said: “We knew this could happen, and so we have a straight-forward, clear plan.
“We announce a boycott of the election. The process in which we are called to participate is not a real election. It will feature only Putin and the candidates which he has personally selected.”
Despite Mr Navalny’s show of defiance, polls show Vladimir Putin is on course for a comfortable re-election, which would keep him in office for another six years.