The trial has resumed in the case against a Russian opposition leader who led protests against President Vladimir Putin and exposed alleged corruption in his government.

Alexei Navalny was back in court on Wednesday accused of heading an organised criminal group that embezzled $500,000 worth of timber from a state-owned company.

The charges not only threaten to send Navalny to prison, but strike at the essence of his image as an anti-corruption activist.

Navalny insists the charges are an act of revenge for his exposure of high-level corruption and are intended to silence him.

The trial began last week in the northwestern city of Kirov, but was adjourned until Wednesday at the request of the defence, which said Navalny had not been given enough time to read the case files.