Two out of five men suspected of killing Russian opposition leader Boris Nemtsov were formally charged in a Moscow court, with one allegedly admitting involvement. A hearing for remaining three suspects was underway. (Reuters)

Two men were charged Sunday with the murder of opposition politician Boris Nemtsov, accused by investigators of taking part in an extor­tionist conspiracy and contract killing, according to courtroom reports. Three others were ­detained.

Russian news agencies reported that at least one of the suspects, Zaur Dadayev, admitted his involvement in the crime to Judge Natalia Mushnikova of Moscow’s Basmanny district court. Dadayev and Anzor Gu­bashev, the two suspects first named by the head of Russia’s federal security service Saturday, were ordered into custody until April 28. No additional details were given about the role they are alleged to have played in the attack.

The other suspects — Shagid Gubashev, Ramzan Bakhayev and Tamerlan Eskerkhanov — were ordered detained until early May, according to news reports from the courtroom.

But questions remain as to who orchestrated the attack and why Nemtsov was killed days before he was scheduled to lead an “anti-crisis” march in Russia.

Russian media reports have said that the five suspects are ethnic Chechens. Chechnya is a mainly Muslim region of the North Caucasus that was the scene of two bloody wars over the past 20 years. The region is controlled by Ramzan Kadyrov, a former separatist and now Kremlin ally who claims his heavy-handed leadership has kept ­Islamist extremism in the region in check.

One of the suspects — Dadayev — was reported to have served as a police officer in Chechnya, ­according to Russian news ­reports citing Albert Barakhayev, a security official in the neighboring region of Ingushetia.

The Russian news service Interfax reported that a sixth potential suspect died in a standoff Saturday night with police in the Chechen capital of Grozny, throwing a grenade at officers who surrounded him and killing himself with another. Investigators are still looking for others who may have been involved in the attack on Nemtsov.

[See: Russians rally for slain Putin critic]

The court proceedings did not offer any clues as to why apparent hit men from Chechnya had allegedly targeted one of Russia’s most well-known opposition figures. But Kadyrov has declared that he will help forestall any protest movement in Russia similar to the uprising in Ukraine last year. Nemtsov had been a strong critic of Russian President Vladimir ­Putin’s intervention in Ukraine and was preparing to publish a report on Russian military ­activity there.

North Caucasus residents have been named as suspects in attacks on other Kremlin critics in the past, most notably in the 2006 murder of Russian journalist Anna Politkovskaya.

Five men from the North Caucasus were convicted in that case last year, but her supporters assert that those who ordered Politkovskaya’s murder are still free.

Similarly, Nemtsov’s allies in the opposition have expressed doubts that those responsible for his death will be brought to justice. Some offered cautious hope Saturday that the detentions — now arrests — would lead to positive developments in the case.

“We hope that they detained those who really are related to the murder, that it is not a mistake,” Ilya Yashin, one of Nemtsov’s closest allies in the opposition, said to Interfax.

Nemtsov’s allies think he was killed because of his opposition to the Kremlin.

Nemtsov, 55, was shot four times in the back while crossing a bridge near the Kremlin — one of the most heavily policed areas of the country — on Feb. 27 with a female companion. Surveillance footage broadcast on a Moscow television station the next day showed assailants disappearing in a car. It also showed that it took 11 minutes for an emergency vehicle to arrive on the scene.

Even those members of the opposition not willing to go so far as to blame the Kremlin for playing a direct role in Nemtsov’s killing have pointed to a climate made more dangerous by officially sanctioned anti-opposition rhetoric. A year ago, Putin warned of a “fifth column” and “national traitors” seeking to undermine Russia from within. Since then, many Kremlin critics have felt targeted, some even fearing for their lives.