Former deputy prime minister and Union of Right Forces (SPS) presidential candidate Boris Nemtsov speaks during an interview at Echo of Moscow radio station in Moscow in this December 26, 2007 file photo. The Russian opposition politician and former deputy prime minister Nemtsov has been shot and killed by four shots in central Moscow. [Photo/Agencies]

MOSCOW - Two suspects have been detained over the killing of Boris Nemtsov, Russian officials said, a week after he was shot dead near the Kremlin in the most high-profile killing of an opposition figure in years.

The Investigative Committee, the state body leading the investigation, named the two men as Anzor Gubashev and Zaur Dadayev. Russian President Vladimir Putin had been informed of the detentions, officials said.

"The individuals detained are, according to our investigation, involved in the organisation and execution of the killing of Boris Nemtsov," the committee said in a statement.

Russian state-controlled media reported the two were from the Caucasus, a violent and impoverished region on Russia's southern flank. They were expected to be formally arrested at a court hearing in Moscow on Sunday, the reports said.

Since Nemtsov was shot dead on the night of Feb 27 as he walked home near Red Square, his friends have said they suspect the Kremlin of involvement. Russian officials deny it.

Associates of the 55-year-old Nemtsov said they would only be satisfied when whoever masterminded the killing was behind bars, not just the people who carried it out.