The two bombs in the Moscow subway blasts that killed 37 and injured at least 65 people had the equivalent of up to 4 kg and 2 kg of TNT, the Federal Security Service (FSB) director said on Monday.
The first attack took place at 7:52 a.m. (03:52 GMT) at the Lubyanka station, located a short distance from the FSB headquarters. The second bomb detonated some 40 minutes later at the nearby Park Kultury station, within walking distance of the Kremlin.
Alexander Bortnikov said the bomb at the Lubyanka station exploded with a force of up to 4 kg of TNT and the second, at Park Kultury, had between 1.5 kg and 2 kg of TNT.
He added that in both cases the bombs were packed with metal nuts and bolts meant to increase the destructive nature of the blast.
A police source earlier told RIA Novosti that the bomb was detonated at a height of 100-200 cm and was apparently attached to the waist of a female suicide bomber.
Bortnikov, said terrorists from Russia's volatile North Caucasus may have been responsible for the blasts. He said the bodies of "two female suicide bombers who were residing in the North Caucasus had been found at the explosion sites."
Russian President Dmitry Medvedev has called for tightened security across the country in the light of the attacks.
MOSCOW, March 29 (RIA Novosti)