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(CNN) —  

Five Chechen men have been found guilty in connection with the murder of Russian opposition figure Boris Nemtsov, according to Russian state news agency Tass.

Nemtsov, a Putin critic who was deputy prime minister in the late 1990s under President Boris Yeltsin, was shot in the back in February 2015 while walking with his girlfriend in central Moscow near the Kremlin.

The trial of the five men began in October 2016. It was heard by a jury at the request of the defendants, at Moscow Regional Military Court. Although most Russian trials are heard by a judge, a jury can be requested in cases of grave offenses such as murder.

Nemtsov was a vocal critic of Putin.
Dmitry Korotayev/Epsilon/Getty Images
Nemtsov was a vocal critic of Putin.

The five men were arrested in March 2015. A sixth suspect blew himself up after a standoff with police in Grozny, the Chechen capital, according to reports on state-run television at the time.

Another suspect – a former officer in the Chechen military called Ruslan Mukhudinov – has been charged in absentia, according to Tass. Mukhudinov has been on the international wanted list since November 2015 and a criminal case against him is being investigated separately, Tass said.

Verdict criticized

Accused Shadid Gubashev stands inside a defendants' cage at a court hearing in Moscow on Tuesday.
KIRILL KUDRYAVTSEV/AFP/Getty Images
Accused Shadid Gubashev stands inside a defendants' cage at a court hearing in Moscow on Tuesday.

Investigators said forensic evidence found in the getaway car and telephone records linked the suspects to the crime.

Four of the accused men, Anzor and Shadid Gubashev, Tamerlan Eskerkhanov and Khamzat Bakhayev, claimed their innocence throughout the case. The fifth, Zaur Dadayev, initially confessed to his role and that of the others in the crime, according to Natalia Mushnikova, the judge in the case, but later told human rights activists from Russia’s federal watchdog, the Public Observation Commission, that he did so under torture and retracted his confession, according to reports from state news agency RIA Novosti.

Zaur Dadayev (R), charged with masterminding and carrying out the killing of Boris Nemtsov, stands in court Tuesday.
KIRILL KUDRYAVTSEV/AFP/Getty Images
Zaur Dadayev (R), charged with masterminding and carrying out the killing of Boris Nemtsov, stands in court Tuesday.

Sentencing is expected next week. The punishment for people convicted of murder ranges from eight years in prison up to life imprisonment, depending on the circumstances, according to Russia’s Criminal Code.

Nemtsov’s daughter, Zhanna Nemtsova, criticized the verdict in a Facebook post, saying that “the case remains unsolved.”

While five men have been convicted of her father’s murder, investigators have not established who ordered the killing, she said.

“People in Russia and in the world are convinced of the political background to the murder, and our [the Russian] investigation and the court deny the obvious. Furthermore, they failed to establish any motive for murder. This just clearly shows the blatant falsity of our state,” she wrote.

02:44 - Source: CNN
Nemtsov's daughter: Russia has crossed a line

Before the trial, investigators said the suspects were allegedly angered not by Nemtsov’s opposition to the Kremlin, but by his support for murdered cartoonists who drew the Prophet Mohammed at the French magazine, Charlie Hebdo. The magazine was the scene of a massacre in January 2015.

Related story: Russian protesters mark anniversary of Boris Nemtsov’s death

Mysterious deaths

Several critics of President Vladimir Putin and the Russian government have been killed or injured in mysterious circumstances in recent years.

They include Denis Voronenkov, a one-time member of Russia’s lower house of parliament for the communist party, who died in March 2017 after being shot outside a hotel in Kiev. The investigation into his killing continues; nobody has yet been charged.

Vladimir Kara-Murza, an anti-Putin activist and friend of Nemtsov, has fallen into a coma twice in the past two years. Both times, his family said he had been poisoned. No criminal case has been opened in relation to the incident.

In 2006, former Russian spy Alexander Litvinenko died a slow death from poisoning in Britain. In a deathbed statement, he blamed Putin for ordering his poisoning with the rare radioactive substance polonium-210, saying it was slipped into his tea at a London hotel.

A detailed UK inquiry later concluded that Putin probably approved the operation by Russian agents to kill Litvinenko.

Also in 2006, Anna Politkovskaya, a journalist critical of the Kremlin and of Russia’s war in Chechnya, was gunned down at the entrance to her Moscow apartment block. In 2014, a Moscow court sentenced five Chechen men to prison for their role in her murder. A sixth man, a former Russian police officer, had been jailed in a separate court case in 2012.

Related story: 5 theories on Nemtsov killing

CNN’s Jill Dougherty, Emma Burrows and Mary Ilyushina reported from Moscow and Elizabeth Roberts wrote from London.