Investigators say they are examining several theories as to the motive
A top human rights lawyer who acted for the family of a Chechen woman murdered by a Russian army officer has been shot dead along with a journalist in Moscow.
Stanislav Markelov, who acted for the family of Kheda Kungayeva, 18, was shot by a gunman after a news conference in the centre of the Russian capital.
He had voiced outrage after officer Yuri Budanov was released early.
Budanov was the first Russian officer to be prosecuted for killing a civilian during the conflict in Chechnya.
He confessed to strangling Ms Kungayeva in 2000, saying he had acted in a fit of rage while interrogating her, suspecting she was a sniper.
He was subsequently jailed for 10 years and was released with more than a year of his sentence to serve.
Mr Markelov was shot in the head with a pistol fitted with a silencer not far from the building where he had just held a news conference on the Kungayeva case, law enforcement officials said.
Mr Markelov had said that Russia's legal system was deeply flawed
A newspaper journalist who was with him, Anastasia Baburova from the Novaya Gazeta, was badly wounded in the attack and died a few hours later in hospital.
Investigators say that they are examining several possible theories as to the motive for Mr Markelov's killing, including the possibility that it was linked to his professional activities.
According to the Russian RIA-Novosti news agency, Mr Markelov had just told reporters that he planned to appeal against Budanov's early release.
The municipal court in Dimitrovgrad, where Budanov was serving his sentence, ruled in December that he should be freed early because he had repented his crime.
The decision led to protests in Chechnya attended by both human rights activists and representatives of the pro-Moscow authorities.
In an interview with the BBC's Russian Service a few days ago, Mr Markelov said the decision to release Budanov showed that the Russian system was deeply flawed.
"I understand now that there is no rule of law," he said.
"My task now is to find out who gave the order for Budanov to be released, and to present a criminal case to the chief prosecutor in order to find out who is guilty of breaching their legal authority."
Chechnya has been devastated by heavy fighting since 1994, when Russian troops first poured in to crush a separatist movement.