MOSCOW: A prominent Russian lawyer who spent the better part of a decade pursuing contentious human rights and social justice cases was killed on Monday in a brazen daylight assassination in central Moscow, officials said.

The lawyer, Stanislav Markelov, had just left a news conference where he announced that he would continue to fight against the early release from jail of Yuri Budanov, a former Russian tank commander imprisoned for murdering a young Chechen woman.

Anastasia Baburova, a 25-year-old journalist who was with Markelov, was also killed, according to a spokeswoman for a newspaper where she worked as a freelancer, Novaya Gazeta, which is highly critical of the government. The two were shot.

Officials said they believed that Markelov, 34, was the primary target, having brought cases against the Russian military, Chechen warlords and murderous neo-fascists. With a laundry list of his potential enemies, authorities refrained from naming any suspects.

“Investigators are looking into various theories, including that the murder was linked to the victim’s professional activities,” Vladimir Markin, a spokesman for the investigative wing of the Prosecutor General’s Office, said of Markelov.

The murder bore the characteristics of a contract killing, a not-uncommon phenomenon in Russia. Even so, the audacity of Markelov’s murder surprised some commentators.

“Even when organized crime in the 1990s was rampant, such a killing would have been considered bold and horrific,” said a correspondent from Vesti television.

Markelov, who was the director of the Rule of Law Institute, a civil liberties group, gained prominence recently representing the family of Elza Kungayeva. She was an 18-year-old Chechen whom Budanov, the former tank commander, admitted strangling in his quarters in March 2000, just as the second post-Soviet war in Chechnya was beginning to rage.

Budanov was sentenced to 10 years in prison but was given early parole for good behavior.

Markelov, at the news conference just before his death, told reporters that he might file an appeal to the European Court of Human Rights against the early release of Budanov, who was a decorated colonel of the Russian Army before he was stripped of his rank. In an interview last week with The New York Times, Markelov said he might also file a lawsuit against the administration of the prison that released Budanov last Thursday.

The decision to free Budanov set off street protests and outraged some human rights groups and Chechen officials. It reignited long-simmering tensions years after a decade of intermittent war in Chechnya, a southern Russian republic, was replaced by tenuous stability.

But Budanov was also revered by nationalists as a valiant fighter who helped wage a bloody but necessary war against separatist rebels in Chechnya. Some now see Markelov’s murder as revenge for his efforts against a Russian hero.

“The murder of Markelov, I consider a bold open warning by the ’party of war’ to democratic Russia,” Nudri Nukhazhiev, Chechnya’s human rights ombudsman, said in a statement. “Today, there are no facts or evidence of the direct participation of Budanov in this crime, but I am more than certain that it was committed by his supporters with his consent.”

Markelov phoned the father of Kungayeva, the slain teenager, a few days ago to complain that he had received death threats, the father told the Interfax news agency.

Lela Khamzayeva, another lawyer for Kungayeva’s family, was adamant, however, that the killing of Markelov could not be linked to his connection with Budanov, because his role during the actual proceedings against the former colonel was, as she put it, “insignificant.”

“If someone is trying to link this murder with Markelov’s participation in the Budanov case, well, that’s just ridiculous,” she said.

Given Markelov’s propensity for challenging the Russian authorities and others known to settle scores violently, the list of potential suspects is lengthy.

He worked closely with Anna Politkovskaya, an investigative journalist with Novaya Gazeta and strong critic of Russia’s Chechnya policies, who was murdered in Moscow in 2006.

He often defended the interests of those, like Kungayeva, who became ensnared in the violent and often arbitrary military justice of the Chechen conflict or the tyrannical rule of Chechnya’s violence-prone leader, Ramzan Kadyrov, in the war’s aftermath.

“He handled almost every case opened as a result of the work of Anna Politkovskaya,” said Nadezhda Prusenkova, a spokeswoman for Novaya Gazeta.

While he was not involved in the current trial of three men accused in the murder of Politkovskaya, Markelov did work on the case of another murdered Novaya Gazeta journalist, Igor Domnikov, who died in 2000 from wounds caused by a hammer blow to the head.

Markelov has also represented victims of neo-fascist and xenophobic violence, a phenomenon that has been expanding annually both in frequency and intensity, according to experts.

At least 10 people were killed and 9 others injured in racist attacks in Russia in the first two weeks of 2009, said Aleksandr Brod, the head of the Moscow Human Rights Bureau, Interfax reported.

Baburova, the freelancer who was killed Monday, began working for Novaya Gazeta last October. She cited Markelov in her most recent article about fascist groups, published on Saturday.

In it, the lawyer criticized the authorities for their handling of a case against the leader of a violent nationalist group, who was sentenced to three years in prison for arranging the murder of a man from Tajikistan and putting video of the killing on the Internet.

With Baburova’s death, Novaya Gazeta has lost four reporters to murder or other mysterious circumstances since 2000.