A crowd of journalists gathered Sunday outside a Moscow courthouse, expecting to see the suspects in the murder of well-known Russian opposition figure Boris Nemtsov arraigned there. Security around the Basmanny district court had been stepped up, with large numbers of police lining the streets and guarding the entrances.

Reporters said two buses arrived at the court on Sunday and drove to its back entrance, but it was not possible to identify who was being delivered (pictured above). Later, court spokeswoman Anna Fedeeva told journalists five suspects had been delivered to the court for arraignment.

Nemtsov, a former deputy prime minister of Russia and a prominent critic of Russian President Vladimir Putin, was shot dead while walking within sight of the Kremlin on February 27. Denouncing the killing as a "provocation," Putin vowed those responsible would be brought to justice.

On Saturday, the head of Russia's FSB security service Alexander Bortnikov announced on national television that two suspects from Russia's North Caucasus region had been detained. He named them as Anzor Gubashev and Zaur Dadaev. Russian state news agencies reported Dadaev had worked for 10 years in the security forces in the turbulent republic of Chechnya, while Gubashev had worked for a private security firm in Moscow.

Russian agencies quoting Albert Barakhayev, Security Council secretary in the Ingushetia republic, reported some members of the men's families lived in the area. There had been reports of at least two other suspects having also been detained, including a relative of Gubashev, though no other suspects have as yet been named by those investigating Nemtsov's murder.

There were also reports carried by Russia's Interfax news agency which quoted a Chechen law enforcement source as saying a man killed in a standoff with police in the Chechen capital late Saturday was also wanted in connection with the Nemtsov probe. According to Interfax, quoted by news agency Reuters, when police arrived at an apartment block, the man threw one grenade at officers and then blew himself up with a second.

se/rc (Reuters, AP, AFP)