Opposition supporters will march through Moscow on Sunday in memory of Kremlin critic Boris Nemtsov, whose murder has increased concern about Russia's future among opponents of President Vladimir Putin.
U.S. Secretary of State John Kerry said on Wednesday additional sanctions against Russia are "teed up" should events in eastern Ukraine warrant them, and he suggested a decision may come soon.
Ousted Ukrainian President Viktor Yanukovich, who fled to Russia a year ago after being toppled by months of street protests, said he was ready to return to Ukraine if the opportunity arose.
Germany condemned the seizure of a strategic east Ukrainian town by pro-Russian rebels on Wednesday as a "massive violation" of a ceasefire, but said it was too early to call the broader Minsk peace plan dead or ratchet up sanctions against Moscow.
