MOSCOW -- Two suspects have been detained in the killing a week ago of opposition politician Boris Nemtsov, the head of Russia's federal security service said Saturday. Russian news reports later cited an official as saying one of them had served with police troops in Chechnya.
The short and vague announcement of the detentions by Federal Security Service director Alexander Bortnikov prompted only skepticism and weak satisfaction from Nemtsov's comrades.
Bortnikov, in comments shown on state television, said the two suspects were from Russia's North Caucasus region, but gave no details other than their names.
He said they were "suspected of carrying out this crime," but it wasn't clear if either of the suspects was believed to have fired the shots that killed Nemtsov as he and a companion walked over a bridge near the Kremlin on Feb. 27. No charges were immediately announced, but the two were expected appear in a Moscow court on Sunday.
Bortnikov didn't say where the detentions took place, how they were conducted or what led agents to the suspects.
However, the state news agencies Tass and RIA Novosti said they were detained in Ingushetia, a republic bordering Chechnya, citing Ingush Security Council chief Albert Barakhoev.
One of them, Zaur Dadaev, served in a battalion of Interior Ministry troops in Chechnya, Barakhoev was quoted as saying. He said the other, Anzor Gubashev, had worked in a private security company in Moscow, according to the reports.
Barakhoev also was quoted by RIA Novosti as saying two others were seized at the same time as the suspects. But there has been no official announcement of their detention. Dadaev's mother, Aimani, was quoted by the Interfax news agency as saying the two others were her nephews.
Nemtsov's killing shocked Russia's already beleaguered and marginalized opposition supporters. Suspicion in the opposition is high that the killing was ordered by the Kremlin in retaliation for Nemtsov's adamant criticism of President Vladimir Putin. The 55-year-old Nemtsov was working on a report about Russian military involvement in the eastern Ukraine conflict.
But Russia's top investigative body said it was investigating several possible motives, including that he was killed in an attempt to smear Putin's image. It also said it was looking into possible connections to Islamic extremism and Nemtsov's personal life.
Chechnya, where Dadaev reportedly worked, was wracked by two wars over the past 20 years between Russian forces and separatists increasingly allied with fundamentalist Islam. Although the insurgency died down in Chechnya several years ago, attacks attributed to Islamic militants sporadically occur in nearby regions.
Chechnya's strongman Kremlin-backed president Ramzan Kadyrov has imposed an Islam-tinged rule on the region, including the mandatory wearing of headscarves by women. Kadyrov, himself a former rebel, has been widely accused of rampant human rights abuses including executions and abductions of opponents.
Many believe that Nemtsov's death in a tightly secured area near the Kremlin wouldn't have been possible without official involvement, and could be an attempt to scare other government foes.
Putin, who had dubbed Nemtsov's killing a "provocation," made no comment on the detentions announced Saturday.
One of Nemtsov's closest allies in the opposition, Ilya Yashin, said on Facebook that "It's hard to judge whether these are the real performers or if the investigation went down a false track."
In any case, he said, "it's extremely important that the matter not be limited to detention of the shooters, whether these are the real killers or not. The key task is the identification and detention of who ordered" the attack.
"For the time being, it's very skimpy information, which tells us little, but it's good that the first results of the investigation has appeared," another opposition leader, former Prime Minister Mikhail Kasyanov, was quoted as telling the news agency Interfax.
In some previous killings of Kremlin critics, especially the murder of journalist Anna Politkovskaya in 2006, there has been wide criticism that those who ordered the killing haven't been identified or prosecuted.
Four Chechens were among the five convicted in Politkovskaya's killing, which was widely believed to be in retaliation for her criticism of Kadyrov and Russia's actions in Chechnya.
Kremlin critics say the spiteful nationalist propaganda on state television, which cast Nemtsov and other liberals as Western stooges, helped prepare the ground for his killing.
Armed with flowers and flags, tens of thousands turned out Monday in a somber but defiant display of solidarity with Nemtsov. Some carried banners that read "I am not afraid." But CBS News correspondent Clarissa Ward reports, in reality, many democracy activists in Russia acknowledge privately that they are now afraid.
Opposition leader Vladimir Ryzhkov was close friends with Nemtsov for more than 20 years. He said Monday that he can't remember the last time the atmosphere in Russia was as aggressive and negative as it is at present.
"This atmosphere was created by Kremlin propaganda for the last year," Ryzhkov told Ward. "I blame state and state propaganda for creating such kind of pro-violence, pro-terror and public atmosphere in country."
No matter who pulled the trigger, Ryzhkov said, the message was clear: Those who speak out against Putin can be targeted.
"I think that nobody knows, not only what future for opposition we have, no one can say what future for Russia we will have," Ryzhkov told CBS News.
Nemtsov was walking with a young Ukrainian woman, Anna Duritskaya, when he was shot. The woman has returned to Ukraine after questioning by police and the state news agency RIA Novosti on Saturday quoted her lawyer Vadim Prokhorov as saying she hasn't been called back to Russia for testimony in connection with the detentions.