Two suspects have been detained in relation to the murder of Russian opposition leader Boris Nemtsov.
"I would like to inform you that the work that has been conducted has resulted in two suspects in this crime being detained today," said Alexander Bortnikov, the head of the Federal Security Service.
“They are a Gubashev, Anzor and a Dadayev, Zaur,” he said in a video posted on state TV Channel One’s website.
No further details were provided about the suspects, but RIA Novosti news agency quoted Mr Bortnikov as saying that both were from the Caucasus.
Mr Bortnikov told Channel One that Russian president Vladimir Putin had been informed of the detention and that the investigation was ongoing.
Mr Nemtsov (55), was shot dead near the Kremlin late on Friday, February 27th, as he was walking home and many European politicians and diplomats attended his funeral in Moscow on Tuesday.
The Kremlin has denied accusations that it played a role in his death.
Mr Nemtsov, a former deputy prime minister and one of Mr Putin's most vehement critics, was killed hours after a radio interview in which he denounced the president for his "mad, aggressive" policies in Ukraine.
Before his death, Mr Nemtsov was working on a report about Russian involvement in the war in eastern Ukraine.