Russian members of parliament have furiously accused the government of losing the battle against crime a day after the killing of leading liberal politician.
Investigators say Yushenkov died from a single shot to the chest
"It's painful, shameful and frightening to live in our country," said Alexander Gurov, a former police investigator who is now a member of parliament for the Yabloko Party.
Sergei Yushenkov, a co-chairman of the Liberal Russia party, was gunned down at the entrance of his Moscow apartment block on Thursday evening.
He was the ninth member of parliament to be shot dead in as many years.
None of the cases have been solved.
1994: Andrei Aizderdzis, Valentin Martemyanov
1995: Sergei Skorochkin, Sergei Markidonov
1998: Lev Rokhlin, Galina Starovoitova
2001: Mikhail Sirota
2002: Vladimir Golovlev
2003: Sergei Yushenkov
A Communist member of the lower house of parliament, Ivan Nikitchuk, said President Vladimir Putin should be called to account.
"Let him tell us who is ruling the country: bandits, the Mafia, or the president," he said.
Yushenkov's murder, by a single shot to the chest, is seen by Russian politicians and journalists as a political assassination.
Unlike fellow Liberal Russia party chairman Vladimir Golovlev, who was shot dead in August, he appears to have had no business interests.
The leader of the Union of Right Forces, Boris Nemtsov, said: "Sergey was a man with a blameless reputation, a fact that even his political enemies acknowledged."
We must demand an honest answer from the authorities: What do you need today to fight crime, even street crime, even banditry, to say nothing of corruption and organised crime, to save people from hooligans?
Investigators say they have no suspects so far.
One member of Liberal Russia, Yuly Rybakov, speculated in the Moscow Times newspaper that Yushenkov could have been killed for his attempts to show that the security services were guilty of a series of apartment-block bombings in 1999.
The bombings, officially blamed on Chechen warlords, helped to stimulate public enthusiasm for the return of Russian troops to the breakaway republic later that year.
Another co-chairman of the party, Viktor Pokhmelkin, was quoted by the Kommersant newspaper as saying that Yushenkov's most serious conflict now was with the Russian tycoon, Boris Berezovsky.
He added, however: "I would not dare to think that these disagreements could be a reason for murder. That would be monstrous."
Mr Berezovsky told Kommersant: "Whatever my disagreements with Sergei may have been, he is after all my comrade. I'm lost for words."
Yushenkov was killed hours after Liberal Russia had been registered by the Justice Ministry, giving it the green light to run in December's parliamentary election.
The party was set up in 2002 with Mr Berezovsky's financial and political support - but he was expelled in the autumn for wooing the Communist Party.
Mr Berezovsky reportedly gained the support of some of the party's provincial branches, causing a split.
But it was the section of the party under Yushenkov's leadership that won official registration.
Western businesses in Moscow said the murder served as a reminder that while President Putin had brought a degree of stability to Russia he had failed in his attempt to establish a "dictatorship of law".