Yury Budanov, the former commander of a tank regiment during the second military campaign in Chechnya, was convicted in the summer of 2003 of strangling an 18-year-old Chechen woman, Elsa Kungayeva, three years earlier and was sentenced to 10 years in jail.
A court in the Volga basin's Ulyanovsk Region upheld his parole request on December 24. Budanov, whose parole had been rejected once by the same court, will be freed after January 11 some 15 months early.
More than 1,000 people took to the streets of Grozny the day after the ruling to protest the decision.
The second protest rally on Monday was attended by some 100 people, the local Interior Ministry said. The protesters demanded that the ruling be overturned.
An uncle of the killed Chechen woman, Lema Kungayev, who has slammed the ruling, also took part in the protest.
"The fact that the rapist and killer is released today shows that the Russian court system has double standards when it comes to serious crimes committed in Chechnya by Russian soldiers. I'm strongly in favor of criminals serving their time," Kungayev said.
The chairman of Russia's Supreme Court, Vyacheslav Lebedev, said on Friday he may be involved in any appeal against Budanov's parole.
"Undoubtedly, each citizen is entitled to appeal, including to the Supreme Court, on issues of judicial defense," Lebedev said. "I can not talk about this particular case, because I am not the judge, but I am not ruling out that I could be the one to hear this case."