A woman holds a photograph of recently killed reporter Anna Politkovskaya, with the words 'The Kremlin has killed freedom of speech'

The United States is urging Russia to conduct a thorough investigation into the killing of a noted journalist and Kremlin critic who was shot Saturday in Moscow.

In a statement Sunday, the White House saluted the courage of Anna Politkovskaya and her efforts to shine a light on human rights abuses and corruption, especially in Chechnya, as it called on Russia to bring justice to those responsible for her murder.

Colleagues of the award-winning journalist say her witness accounts and photographs of tortured bodies in Chechnya are to be published Monday in the Novaya Gazeta (New Journal) newspaper.

Hundreds of mourners lit candles and laid flowers outside Politkovskaya's Moscow apartment her newspaper's offices. One protest poster alleged "the Kremlin has killed freedom of speech."

The Itar-Tass news agency says the crime showed clear signs of a contract murder. Security video footage from the building showed a tall suspect wearing dark clothing and a dark baseball cap.

In an interview Thursday with Radio Free Europe, the reporter said she was a witness in a criminal case against Moscow-backed Chechen Prime Minister Ramzan Kadyrov.

In April, she told The New York Times she had evidence of torture by Mr. Kadyrov's police and other gunmen. She told the Times at least one witness had been tortured by Mr. Kadyrov himself. The prime minister has denied the allegations.

Former Soviet President Mikhail Gorbachev, a shareholder in the Novaya Gazeta newspaper, called the killing "a savage crime and a blow to the entire democratic, independent press."