The editor of the Russian edition of the financial magazine Forbes has been shot dead near his office in Moscow.
Paul Klebnikov's employer described him as a courageous reporter
Paul Klebnikov, 41, was shot four times in the street at about 2200 (1800 GMT) on Friday and died in an ambulance on the way to hospital, police said.
Reports say shells of different calibre were found at the scene of the shooting, indicating that there were at least two attackers.
The US citizen was an outspoken critic of Russia's wealthy oligarchs.
Alexander Gordeyev, the editor of Russia's Newsweek magazine, which shares the same building as Forbes, rushed to Mr Klebnikov's side after the shooting.
"I asked Paul several times why he thought this had happened," Russia's Interfax news agency quoted him as saying.
"Paul said he didn't know. He told me several times nothing suspicious had happened to him," Mr Gordeyev said.
Mr Klebnikov died a short time later.
The Russian edition of the US Forbes journal, which spotlights powerful celebrities, was launched earlier this year.
It published a list of the country's wealthiest people and claimed that Moscow had more billionaires than any other city in the world.
Mr Klebnikov, born in New York to Russian immigrants, had worked for Forbes for at least 13 years.
He wrote a controversial article in 1996, questioning the honesty of exiled Russian businessman Boris Berezovsky.
Mr Berezovsky filed a libel suit and the magazine was forced to retract allegations made in the article.
In 2001, Mr Klebnikov published a best-selling book, Godfather of the Kremlin, which was also highly critical of Mr Berezovsky.
Mr Berezovsky is wanted on fraud charges in Russia, but has been given asylum in Britain and has changed his name.