Vladimir Putin's arch-enemy Mikhail Khodorkovsky was facing renewed pressure on Tuesday as Russian investigators summonsed the exiled former oil tycoon for questioning in a recently resurrected murder case.
Mr Khodorkovsky, the founder of the now defunct Yukos oil corporation, served 10 years in a Siberian jail after being arrested in 2003 on charges of financial wrongdoing that his supporters say were fabricated by the Kremlin to thwart his political ambitions.
He received a pardon from Mr Putin in late 2013 shortly before the expiry of his prison term, and has been living in Switzerland ever since.
On Tuesday, Mr Khodorkovsky tweeted a copy of a summons from the Russian investigation committee naming him as a defendant in a case relating to the murder in 1998 of Vladimir Petukhov, the mayor of Nefteyugansk, an oil town in Siberia where Yukos was once based.
Mr Khodorkovsky said the summons had been delivered to his 82-year-old father who still lives in Russia, and was himself subjected to interrogation by the investigation committee earlier this year.
Life sentence
A Moscow court handed a life sentence to Alexei Pichugin, the former head of Yukos's security department, in 2007 for organising Petukhov's killing. Various western organisations, including the Council of Europe and the European Court of Human Rights, have criticised the handling of Pichugin's trial.
Russian investigators reopened the case in June, saying evidence had surfaced that Mr Khodorkovsky may have ordered the crime.
The summonsing of Mr Khodorkovsky comes at a difficult time for the Russian authorities, facing growing criticism for corruption from political activists and the public.
Russian truck drivers have been staging nationwide protests for more than three weeks against a crippling new road toll which they say will enrich oligarchs with close connections to the Kremlin.
In a separate development, Russian opposition activists published the results of an investigation accusing Yuri Chaika, Russia’s prosecutor general, and his family of involvement in criminal business activity.
Navalny fund
The 40-minute film made by opposition leader Alexei Navalny's anti-corruption fund has attracted more than 2.98 million views since appearing on YouTube a week ago and fuelled lively commentary on social networks.
Russian investigators’ move to revisit the Petukhov case and accuse Mr Khodorkovsky of murder was a “classic attempt” by the authorities “to change the news agenda”, Mr Navalny tweeted on Tuesday.
From exile, Mr Khodorkovsky has continued to campaign for political reform in Russia, using his Open Russia foundation as an online platform to unite and embolden the struggling opposition.
Yukos’s former shareholders have also created grave difficulties by winning billions of dollars in legal compensation for losses sustained when the vast Russian oil corporation was dismembered and sold off to state-owned groups a decade ago.
Russia has been battling a ruling by the European Court of Human Rights (ECHR) in July 2014 which ordered it to pay Yukos claimants more than $2 billion in damages over Russia’s seizure of the oil company.
New legislation adopted by the Russian parliament last week places the Russian constitution over international law and could make it impossible for the ECHR to enforce the penalties.