One of two men arrested and charged in the killing of Russian opposition leader Boris Nemtsov has confessed to involvement in the crime, according to Russian news agencies cited by the Associated Press Sunday. The judge handling the case said Zaur Dadaev made a statement confirming his guilt, but it is unclear to which crime or crimes he confessed.

Dadaev served about 10 years in the so-called Sever battalion of Chechnya's interior ministry, Russian state-controlled news agencies reported.

Both Dadaev and Anzor Gubashev have been charged in the Feb. 27 killing of Nemtsov, who was shot while walking on a bridge near the Kremlin in Moscow. However, Gubashev told the judge he is not guilty.

Meanwhile, the judge ordered the jailing of three other suspects in the case, AP reported. They are Gubashev’s brother Shagid Gubashev, Tamerlan Eskerkhanov and Khamzad Bakhaev. Dadaev and the Gubashevs were arrested in Ingushetia Saturday, while Bakhaev and Eskerkhanov were detained in Moscow Sunday, AP reported. None of them has been charged.

Nemtsov’s slaying shocked many in Russia, and some in the country’s opposition suspect the killing was ordered by the Kremlin in retaliation for Nemtsov's adamant criticism of President Vladimir Putin, as well as to forestall a report he was preparing about the extent of Russia’s military involvement in Ukraine. The report will be completed and published, anyway, opposition activists have said.

Ilya Yashin, a close ally of Nemtsov’s and a prominent figure in the Russian opposition, told the Times newspaper in the U.K. that evidence collected by Nemtsov, which the opposition leader alleged included the testimony of the parents of Russian soldiers killed fighting in Ukraine, was still available to the opposition.