A friend of slain Russian opposition activist Boris Nemtsov on Monday dismissed theories that radical Islamists were responsible for gunning him down as "absurd" and politically motivated.
Investigators have said they were looking into the possibility that the former deputy prime minister was killed over his support for French satirical magazine Charlie Hebdo which published images of the Prophet Mohammed.
The theory appeared to gain ground after a suspect from Russia's Muslim North Caucasus region of Chechnya -- which held a massive rally against the publication in January -- confessed to his involvement in the assassination.
"The official version of the inquiry is more than absurd. In my opinion it is the result of a political order from the Kremlin," Ilya Yashin, who co-founded the opposition movement Solidarnost with Nemtsov, told AFP.
He said Nemtsov had "never spoken negatively about Islam" and had merely criticised the Islamists who gunned down 12 people at Charlie Hebdo's offices in a series of attacks in Paris in January.
Zaur Dadayev, a former deputy commander in a special Chechen police unit, was charged with murder on Sunday alongside Anzor Gubashev who worked for a private security company in Moscow. They, along with three other suspects, were remanded into custody.
A court in Moscow heard the men were being probed under a section of the Russian criminal code relating to murders carried out for financial gain, in a sign investigators believe Nemtsov's murder was a hit.
"Our worst fears are coming true: the hitman has been arrested but the commander will remain free," Yashin added.
Chechen leader Ramzan Kadyrov said he was baffled by the arrest of a man who was "one of the bravest and worthiest soldiers of his regiment" and called a probe into reasons for Dadayev's dismissal from the unit.
"All those who know Zaur, are saying that he is a deeply religious person and that he, as well as all Muslims, was shocked by what Charlie (Hebdo) did and by comments in support of continuing the printing of the caricatures," Kadyrov wrote on Instagram.
Putin on Monday awarded Kadyrov an order of merit for "work successes," the latest in a number of Kremlin decorations for the controversial strongman leader.
Charlie Hebdo's publication of an image of the Prophet Mohammed following the January attack angered many in the Muslim world.
The 55-year-old Nemtsov, an outspoken critic of Putin, was shot four times in the back on February 27 as he walked along a bridge with his girlfriend near the Kremlin.
The killing sent shivers through an opposition that accuses Putin of steadily suppressing dissent, and accused the Kremlin of being behind the murder of one of its last outspoken critics.
Investigators have said they were also probing the possibility he was assassinated for criticising Russia's role in the Ukraine conflict or as part of a plot to destabilise the country.