Terrorists from Russia's volatile North Caucasus may have been responsible for Monday morning's blasts in the Moscow metro, the head of the country's Federal Security Service (FSB) said.
The explosions, the first in the Moscow metro since February 2004, killed at least 36 people.
Russia's top investigator Vladimir Markin said police may be able to identify the two female suicide bombers who carried out the attacks. He added that the women's faces had not suffered in the blasts.
The first attack took place at 7:52 a.m. (03:52 GMT) at the Lubyanka station, located a short distance from the headquarters of the Federal Security Service (FSB), and killed at least 23 people, with another 18 injured.
The second blast detonated some 40 minutes later at the nearby Park Kultury station, within walking distance of the Kremlin. At least 12 people lost their lives and 15 were injured.
Markin earlier told journalists that the second attack had been carried out by a "dark-haired woman" and that "fragments of her body" found at the scene suggested she had had the equivalent of 1.5 kg of TNT strapped to her waist.
A police source earlier told RIA Novosti that "An inspection of the scene indicates that the bomb was detonated at a height of 100-200 cm and was apparently attached to the waist of a female suicide bomber."
Russian President Dmitry Medvedev has called for tightened security across the country in the light of the attacks.
Police with sniffer dogs are carrying out inspections of other stations as the capital remains on high alert. Security has been tightened at Moscow's overland train terminals and airports.
With central Moscow at a standstill, the injured are being ferried to hospitals across the capital by helicopter. Police have appealed for calm.
Russia has been fighting militants in the North Caucasus for over a decade, including two brutal separatist wars in Chechnya. Analysts suggest Monday's attacks are revenge for a recent operation in Chechnya that saw the deaths of over 20 radical Islamic fighters.
Aside from Chechnya, violence is also a regular occurrence in the neighboring republics of Ingushetia and Dagestan.
The French and the German foreign ministries have condemned the attacks.
"We deplore these cowardly attacks in the most resolute manner," a statement by the German Foreign Ministry said. "Nothing can justify these vicious acts."
"France resolutely denounces these terrorist acts and assures Russia in its full support," the French statement read.
Ukrainian President Viktor Yanukovych said Russia's neighbor "shared" its loss.
If terrorism is confirmed as the cause of the blasts, this will be the first major terrorist incident in the Russian capital since the autumn of 2004, when ten people were killed in a suicide bomb attack outside a north Moscow metro station.
The explosion was part of a series of terrorist attacks that also saw 90 people die in two plane bombings and the deaths of over 300 people, many of them children, when Chechen terrorists seized a school in Beslan.
A bomb also hit a Moscow-St. Petersburg express train last November, killing 27 people.
MOSCOW, March 29 (RIA Novosti)