Russia is poised to hold its annual Victory Day parade in Moscow’s Red Square amid a surge of patriotism kindled by its annexation of Crimea.
A similar event marking the Soviet victory in World War Two will be held in the Crimean port of Sevastopol.
Russian media reported that President Vladimir Putin might go there, but his spokesman would not confirm that.
Festivities in Ukraine will be muted amid fears of provoking further violence in the south and east.
Moscow denies fomenting separatist unrest in Ukraine.
German Chancellor Angela Merkel said it would be a “pity” if Mr Putin were to “use” the commemorations to visit Crimea.
The BBC’s Steve Rosenberg in Moscow says Russia has experienced a wave of patriotism following its annexation of the peninsula from Ukraine in March.
It is encouraged by the Kremlin, he says, and fuelled by rousing reports on state-controlled TV and radio.
The parade in Moscow traditionally features a display of military hardware and a show of patriotic fervour on Red Square.
However, Ukraine’s interim authorities have discouraged public gatherings amid fears that pro-Russian activists might try to stoke violence.
“Roadblocks have been set up around our capital, where serious checks are being carried out, because we expect that provocative actions may occur on May 9,” said Ukraine’s acting President Olexander Turchynov.
A low-key wreath-laying ceremony is planned in Kiev.
Nazi Germany invaded the USSR – which included Ukraine – in June 1941 and advanced almost as far as Moscow before being driven back to Berlin in some of the fiercest fighting of the war.
Russia estimates that 26.6 million Soviet citizens were killed in the war, about 8.7 million of them members of the armed forces.
Pro-Russian separatists in eastern Ukraine say they will go ahead with independence referendums on Sunday, despite a call from President Putin to postpone them.
The decision was announced by separatist leaders in the regions of Donetsk and Luhansk on Thursday.
Activists remain in control of many official buildings across the south and east despite a military operation by Kiev to remove them. Dozens of people have been killed in the unrest.
Moscow insists it has a right to protect Ukraine’s Russian-speaking population against what it calls an undemocratic government in Kiev. However, Mr Putin had called for the referendums on autonomy to be postponed to create the conditions for dialogue.
Mr Putin also said he was removing troops massed along Russia’s border with Ukraine, but Nato says it has seen no sign of a withdrawal.
Ukraine is preparing for elections on 25 May following the ousting of pro-Russian President Viktor Yanukovych in February by pro-Western protesters.