The bomb explosion has killed businessman and injured 4 other people at Moscow center, officials said.
The explosive device, placed in a parked motorcycle, went off shortly before noon with the force of some 500 grams (17 ounces) of TNT, the Prosecutor General's Office said in a statement.
The blast occurred outside the office of a private company and killed the company's director, the statement said. Four people were hospitalized with injuries of varying severity.
Deputy Moscow Prosecutor Alexei Grigoryev said the blast could have been the result of a business dispute, suggesting the victim may have been targeted in a contract killing. He said there was no evidence of terrorist intentions.
An Internet business-information site indicated the company, Blagvest, is involved in trade. There was no answer at the phone numbers listed.
Contract killings are common in Russia.