Updated at 1:45 p.m. ET
A day after announcing the arrest of two suspects in the killing of Russian opposition leader Boris Nemtsov, investigators said three more individuals had been detained and that at least two of them are being arraigned in a court in Moscow.
NPR's Corey Flintoff reports that authorities are revealing few details about the case.
"At least some of the men are said to come from the southern Russian region of Chechnya," Corey says.
Russian news media quote police sources as saying one of the men, Zaur Dadayev, whose arrest was announced Saturday, was a 10-year veteran of the Chechen security forces, though it's not clear whether he is still a member.
Voice of America says Dadayev and another suspect arrested on Saturday, Anzor Gubashev, have been formally charged. It says the other three suspects are being questioned.
One of the new arrests is reportedly the brother of Gubashev.
According to Russia's Interfax news agency, a sixth suspect was killed last night in a standoff with police in the Chechen capital.
State news agencies Tass and RIA Novosti say the latest arrests were made in Ingushetia, a republic bordering Chechnya, citing Ingush Security Council chief Albert Barakhoev, The Associated Press says.
As AP notes: "Nemtsov's killing shocked Russia's already beleaguered and marginalized opposition supporters. Suspicion in the opposition is high that the killing was ordered by the Kremlin in retaliation for Nemtsov's adamant criticism of President Vladimir Putin. The 55-year-old Nemtsov was working on a report about Russian military involvement in the eastern Ukraine conflict."
Updated at 10:20 a.m. ET. Suspect Denies Involvement In Killing:
"A judge at a Moscow court on Sunday ordered that Anzor Gubashev, who has been charged over the killing of opposition figure Boris Nemtsov, should be kept in custody until April 28.
"The judge told a court hearing that Gubashev, who was covering his face in the courtroom with a sheet of paper, had denied to investigators that he was involved in the killing. Earlier, the court ordered that four other people detained over the killing be kept in custody."