|Chechen rebel leader Doku Umarov had claimed responsibility for the bombing of Domodedovo airport [EPA]
Russia has arrested two people in connection with the Moscow airport bombing which claimed at least 36 lives.
The teenaged brother and sister of the suspected suicide bomber have been arrested, officials said on Wednesday.
The January 24 bombing of Domodedovo airport was conducted by 20-year-old Magomed Yevloyev, an official working with Russia's top investigative agency in the province of Ingushetia, said on Wednesday.
He spoke on condition of anonymity because he was not authorised to publicly discuss the issue.
Earlier, officials said that the bomber was from the Caucasus, but did not give his name.
Doku Umarov, a Chechen rebel warlord, had claimed responsibility for the attack that also injured more than 180.
Umarov said in a video posted on Monday that many more such attacks will follow if Russia does not allow the Caucasus to become an independent Islamic state governed by Sharia law.
A court in Ingushetia's provincial capital, Magas, ordered the arrest of Yevloyev's 15-year-old brother and 16-year old sister, the official said.
Magomed Khazbiyev, a human rights activist from Ingushetia, condemned the arrest of the underage suspects. "This is absurd and savage - to arrest people only because they are relatives of a suspected terrorist," Khazbiyev told the daily Kommersant.
The ITAR-Tass news agency however, reported that investigators had found traces of explosives used in the airport bombing on the hands of Yevloyev's arrested brother.
Yunus-Bek Yevkurov, Ingushetia's regional leader, said DNA tests proved that Yevloyev was the bomber, while his brother and sister knew of the plan but did not tell their parents, the ITAR-Tass news agency reported.