Russian investigators on Thursday announced the arrests of two suspects in the killings of a human rights lawyer and a journalist who were shot in central Moscow in January.

Investigators identified the suspects as a man and woman in their 20s, but gave no details about their motives or suspected roles in the killings of Stanislav Markelov or Anastasia Baburova.

In briefing President Dmitry Medvedev on the arrests, the director of Russia's security services suggested the suspects were extreme nationalists. He said they belonged to an armed group that was implicated in a recent killing motivated by ethnic hatred.

Markelov, 34, a prominent lawyer whose work had angered nationalists, and Baburova, 25, a journalist walking with him, were shot after leaving a news conference on Jan. 19 in a brazen daytime attack by a lone gunman wearing a stocking-style mask.

Russia has seen a string of contract-style killings of human rights workers and journalists in recent years. Few of the killings are ever solved. In the rare case when people suspected of taking part in a killing are brought to trial, the mastermind is rarely identified.

Prosecutors won court approval Thursday to hold the two suspects for further investigation.

The suspects — Yevgenia Khasis, 25, and Nikita Tikhonov, 29 — appeared in court wearing black stockings over their faces.

Federal Security Services Director Alexander Bortnikov told the president in a televised briefing that the decision to arrest the pair was made Tuesday and that the killer had confessed to the crime. Bortnikov did not specify which suspect he was referring to.

However, the spokesman for federal prosecutors, Vladimir Markin, said investigators were still firming up the evidence against the suspects, who would undergo psychiatric examinations.

The wide array of cases handled by Markelov has provided ample room for speculation on a motive for his killing. He angered radical nationalists, who had threatened him and cheered his killing in Internet chatter after his death, but he also made enemies through his work fighting for victims of rights abuses in Chechnya.

Around the time of his death Markelov was representing the family of a Chechen teenager killed in 2000 by a Russian officer, Col. Yuri Budanov, who had won early release from prison. Markelov was working to put Budanov back behind bars. The officer had become a hero to nationalists during his trial.

He had worked with prominent journalist Anna Politkovskaya, who wrote extensively about abuses in Chechnya. She was gunned down in Moscow in 2006 in a similar killing.

Baburova wrote for Politkovskaya's newspaper, Novaya Gazeta.