Russia has tightened security at polling booths, train stations and markets ahead of elections overshadowed by a commuter-train bombing which killed at least 42 people near rebel Chechnya.
President Vladimir Putin's party, running on a strong law and order platform, is expected to make gains in Sunday's poll due to a weak and divided opposition, but it was unclear if the bloody attack in southern Russia would affect voting patterns.
At least 150 people were also wounded when Friday's suspected suicide bombing ripped through the packed train on Russia's southern edge.
Justice Minister Yuri Chaika pointed the finger at Chechen separatist guerrillas, who denied involvement.
Mr Mr Putin pledged a crackdown and law enforcement agencies said they would step up security across Russia.
Itar-Tass news agency quoted police sources as saying an explosive device was found and destroyed early on Saturday at the railway station of Kavkazskaya, also in southern Russia.
Campaign speeches were banned on the day before polling, in line with the constitution.
On Moscow's streets, many expressed disillusionment and treated the attack as nothing new, much like the election which has yet to fire people's imagination.
"I want to spit on the elections, on the explosion on the train and on the president of Russia," said Mr Nikolai Ivanov, an administrator, walking in one of Moscow's main underpasses.
The election, in which voting starts first in the farthest east of Russia's 11 time zones, is seen as a popularity test for Mr Mr Putin who will face a presidential poll in March next year.
Mr Putin, hoping to secure his first parliamentary majority, called the bomb a bid to destabilise Russia before the vote.
He has made the restoration of firm central state control a major policy plank since taking office. Past guerrilla attacks have served to increase his popularity.
His United Russia party is expected to make gains but analysts were not certain Friday's attack would affect the poll where Chechnya, far from Moscow, has not been a key issue.
Friday's explosion killed students and workers in Russia's north Caucasus region. A local Emergencies Ministry official said a 42nd victim died overnight, a 16-year-old girl.
Whoever was responsible, it reminded Russians that Mr Putin, despite tough talk, has yet to rein in separatist guerrillas in nearby Chechnya.
In 1999, as prime minister he won strong support for his tough stance on security after apartment bombings in Moscow and other cities marred the last parliamentary election campaign.
He later sent troops back to the rebel region to subdue it.
The daily newspaper Kommersantsaid the attack showed heightened security was not working.
"It is clear that sending hundreds of police to patrol the streets does not stop the terrorist attacks," it said.
The United States and United Nations both condemned the bombing as terrorism.