Vladimir Putin, Russia's president, has said the twin attacks that wounded the Islamic leader of the country's main Muslim region of Tatarstan and killed another top cleric happened because no "pre-emptive" measures had been taken.
"There is a need to understand the situation, analyse it and take timely decisions," Putin said on Thursday.
"Taking into account this tragic event, we can say that no pre-emptive steps had been taken," he said in televised remarks at a meeting with parliament leaders.
Ildus Fayzov, who was the Mufti of Tatarstan and the most senior Islamic official in Russia's largely Muslim Tatarstan region, was fatally wounded in a car bomb attack and his deputy killed in a separate shooting.
Fayzov's car was blown up as he left a radio station in the city of Kazan, about 735km east of Moscow, the federal Investigative Committee said in a statement.
His deputy, Mufti Valiulla Yakupov, was shot dead at about the same time at the entrance to his home in Kazan, the committee added.
There were no immediate claims of responsibility for the attacks. Tatarstan, in central Russia, has a large Muslim population.
"This once again reminds us of the fact that the situation in our country is far from ideal," Putin said, adding that he ordered the head of the FSB security service to hunt down and punish those behind the twin attacks.
The motive in this case is unclear, but Vladimir Markin, a spokesman for Russia's Investigative Committee, said both leaders were known for fighting extremism and their professional work was being investigated as one of the reasons for the attacks.
Muslim rebels say they are fighting for a separate Islamic state in the strip of provinces along Russia's southern border and sometimes target mainstream Muslim leaders, who have the backing of regional authorities and Moscow.
But their activities have been mostly contained to the Muslim republics of Chechnya, Dagestan and Ingushetia in the North Caucasus.
Tatarstan has been largely peaceful and is held out as a showcase of religious tolerance in Russia, which as a whole is predominantly Orthodox Christian.