Russian investigators have searched the apartments of several opposition leaders and called them in for questioning, raising tensions on the eve of a large protest against President Vladimir Putin.

Putin has taken a harder line against the opposition since returning to the presidency in May, seemingly no longer willing to tolerate the peaceful protests that brought tens of thousands of people onto the streets of Moscow ahead of the election that handed him a third term.

Investigators spokesman Vladimir Markin confirmed that the apartments searched Monday included those of Alexei Navalny, Sergei Udaltsov, Ilya Yashin and also of television personality Ksenia Sobchak, whose father was Putin's mentor.

Markin said all four have been called in for questioning Tuesday making it difficult if not impossible for them to attend the protest.