In a sign Russia would not soften its assertive energy policy, state-controlled Gazprom cut supplies to Ukraine by a quarter on Monday. Gazprom, whose board is chaired by Medvedev, said supplies to the rest of Europe would not be affected.
Medvedev has spent most of his career in Putin's shadow. He largely avoided campaigning altogether and made few stump speeches, leaving analysts largely in the dark about the extent to which he might diverge from his mentor once in the Kremlin.
"The difference between a Putin Kremlin and a Medvedev Kremlin is likely to involve more change in style than substance, but that itself can actually be rather important," said Roland Nash, head of research at Renaissance Capital.
Referring to widespread perceptions that Medvedev's legal training and younger age may make him less abrasive than Putin, Nash said: "A less combative Kremlin with the same focus on generating economic growth as the principal strategy for a resurgent Russia should be welcomed."
Election observers were less generous.
"DEGRADATION"
Andreas Gross, head of the only Western monitoring mission, told reporters the result broadly reflected voters' wishes but said "there was not freedom" in Sunday's vote.
Russian independent observers Golos said the poll was marred by official pressure to boost voter turnout, ballot stuffing and multiple voting - charges which were immediately rejected by the Central Election Commission (CEC).
"Russia's new political system born in 1989 is now in a state of degradation and has been thrown back to Soviet times," Andrei Buzin, a Golos expert, told a news conference.
CEC chief Vladimir Churov, an old university classmate of Putin's, said nobody had produced any convincing evidence of serious violations and scorned calls for greater transparency.
"What should I do, should I make CEC members work naked?" Churov said in televised remarks.
Riot police in Moscow detained dozens of activists at a banned demonstration and dragged protesters to waiting police buses. Some of the protesters lit flares spreading smoke across a central square, shouting: "Your election is a farce."
In St Petersburg, about 2,000 activists chanted "revolution, revolution," and "Russia without Putin".
