Russian investigators are expected to indict several men with the murder of opposition leader Boris Nemtsov. Five Chechen men had been arrested earlier in 2015 on charges of involvement in opposition leader Boris Nemtsov's killing, while one man who is alleged to have ordered the killing remained at large.

Nemtsov's murder had sent shockwaves among Russia's opposition earlier in 2015. A top opponent of Russian President Vladimir Putin, former Deputy Prime Minister Nemtsov was shot late at night on February 27 as he was walking on a bridge outside the Kremlin in Moscow.

Nemtsov was due to lead a major opposition march and release a report about alleged Russian military involvement in the Ukraine conflict.

Chechen conspiracy?

Suspects Zaur Dadaev, Anzor Gubashev, Shadid Gubashev, Temirlan Eskerkhanov and Khamzat Bakhayev were due to be charged with conducting a contract killing and illegally obtaining, possessing and transporting a firearm, Russia's Investigative Committee said in a statement.

The committee added that another suspect, Ruslan Mukhudinov, was believed to have ordered the murder and had since been placed on an international wanted list. The Russian human rights commission said that Dadaev had probably been forced to confess under torture.

Zaur Dadaev, a former Chechen serviceman, has been the key suspect in the murder from the beginning of the investigation. He reportedly confessed early on in the investigation but then attempted to retract his statement.

Russian media claimed that Dadaev had admitted to killing Nemtsov for insulting both Islam and the leader of Russia's predominantly Muslim republic of Chechnya, Ramzan Kadyrov.

Alleged ringleader Ruslan Mukhudinov is suspected of using a fake passport to travel to the United Arab Emirates, where he is believed to reside currently, Russian state news agency RIA Novosti reported.

The Investigative Committee added that it expected the investigation to wrap up early in 2016.

ss/jil (AP, dpa)