The biggest pro-Kremlin party pulled far ahead of its rivals in Russia’s parliamentary elections today, with partial preliminary results suggesting President Vladimir Putin can tighten his grip over the Duma ahead of his own likely re-election bid.

RUSSIAN stocks tumbled in their biggest decline in over four years amid concern the arrest on Saturday of Mikhail Khodorkovsky, chief executive of AO Yukos Oil Co and the country’s richest man, may scare off investors.

The jailing of Russia’s richest man in what is widely seen as a politically-driven attack on his oil empire could herald a return to Soviet-style repression that is bound to trigger capital flight, media and politicians warned today.