The U.S. State Department is urging Moscow to prosecute those responsible for the murder of prominent Russian journalist Anna Politkovskaya, who was killed five years ago Friday.

State Department spokesperson Victoria Nuland said the U.S. welcomes the recent arrests of suspects in her murder, but that “justice will not be done until all those involved” are identified and prosecuted.

In August, Russian authorities arrested former Moscow police lieutenant Dmitry Pavlyuchenkov, who was charged earlier this month with organizing the murder. The alleged gunman in the case was also arrested in May. But investigators are yet to determine who contracted the killing.

Nuland's statement said that the U.S. honors the legacy of Politkovskaya, saying her reporting on the war in the North Caucasus “brought to light the violation of human rights and the suffering of the victims” of the conflict.

Politkovskaya was internationally renowned for her extensive reports in the Novaya Gazeta newspaper on human rights abuses and corruption in Chechnya and other parts of the Russian Caucasus plagued by a deadly Islamist insurgency. She also was a sharp critic of the Kremlin and its policies in Chechnya, as well as of the republic's leader, Ramzan Kadyrov.

She was gunned down in the elevator of her Moscow apartment building in October 2006.

On Friday, Amnesty International praised Russia for making “some progress” with the investigation into Politkovskaya's murder, but said little progress has been made to increase the safety of journalists who “dare to expose abuses or challenge authority in Russia.”

The Committee to Protect Journalists says 22 journalists and media workers have been killed in Russia since 2000.