He said Monday's attacks were retaliation for a Federal Security Services operation in Dagestan's neighboring republic of Ingushetia in February that killed 18 militants and left four civilians dead.
Two suicide bombers also struck the town of Kizlyar in Dagestan Wednesday, killing 12, including nine police officers.
Authorities believe that Abdurakhmanova and her fellow attacker traveled to Moscow by bus via Kizlyar in Dagestan. President Dmitry Medvedev has called the two attacks this week "links of the same chain" and, during a surprise visit to Dagestan Wednesday, promised "brutal" tactics to deal with the insurgents.
"We must deal sharp dagger blows to the terrorists, destroy them and their lairs," Medvedev, dressed in a black suit over a black T-shirt, told law enforcement officials and local leaders.
The North Caucasus region has seen a spike in violence in the past year between Islamist separatist militants and the authorities. But it rarely spills over into the rest of Russia and is therefore largely ignored.
An express train between Moscow and St. Petersburg was bombed in November, killing 26. Umarov and his "Caucasus Emirate" group claimed responsibility and vowed more attacks would follow.
The National Counter-Terrorism committee Friday said that efforts to "identify and neutralize those who ordered, masterminded and perpetrated the terrorist attacks are continuing."