Anna Politkovskaya was killed as she left her apartment building

Russian TV showed prosecutor general Yuri Chaika telling President Putin of the arrests, informing him that those held would soon be charged.

Mr Chaika said "serious progress" had been made in the investigation into the killing, which was widely condemned.

The journalist, a harsh critic of President Vladimir Putin, was shot dead at her Moscow apartment block in 2006.

At the moment there is no information about the identity of the suspects.

Anna Politkovskaya was killed as she left for work. Closed circuit television footage showed a single gunman carried out the murder.

The BBC's Rupert Wingfield Hayes, in Moscow, says that at the time it was rumoured the killer could have been a member of a Chechen criminal gang or even have a connection to the Russian security services.

The Russian government has always strenuously denied any connection to the murder.

Anna Politkovskaya made her name reporting from Chechnya for Russia's liberal newspaper, Novaya Gazeta.

She was also the author of two books in English, A Dirty War: A Russian Reporter in Chechnya (2001), and Putin's Russia (2004).

Her writing was often polemical, as bitter in its condemnation of the Russian army and the Russian government as it was fervent in support of human rights and the rule of law.