Head of the Russian Federal Security Service (FSB) Alexander Bortnikov said Thursday that masterminds behind the consecutive blasts in Moscow and Dagestan have been identified and are being searched for, local media reported.

"The theory that the terrorist attacks were committed by particular gangs connected with the North Caucasus has been confirmed. We personally know the masterminds of the terrorist attacks. A search operation is being conducted," said Bortnikov at a conference hosted by Russian President Dmitry Medvedev, who was on a surprise visit to the restive North Caucasus republic of Dagestan.

Medvedev at the conference urged broadening counter terrorism measures while making them "more efficient and tougher."

"We have obtained certain materials and detained a number of people. Interrogations are under way, some evidence has been obtained, and analyses are being carried out," said the FSB chief as quoted by the Interfax news agency.

Two female suicide bombers killed 39 in attacks at the Moscow subway system on Monday, which the authorities have linked to militants from North Caucasus.

Two days later, another 12 people, including nine police officers, were killed in two blasts in the Dagestani town of Kizlyar.