About 40 minutes later, the train reached the station, and once its doors opened, the second female suspect detonated the second explosion, killing fourteen commuters.

[19] The two women who carried out the attacks wore explosive belts, presumably using detonation devices set inside their mobile phones and activated by a call to self.

[25][26] This figure was revised upwards from an earlier count of 36 killed, that had consisted of 24 people in the explosion at the Lubyanka station and 12 at Park Kultury.

[27] A high-ranking official of the Black Sea Fleet of the Russian Federation, Captain Viktor Ginkut, was also amongst the passengers killed at Park Kultury station.

[28] His residential registry in Sevastopol, Ukraine has raised the question of his actual nationality, but the Ministry of Foreign Affairs of Russia refused to comment on it.

[30] Around 10:04 am local time a call from a public phone announcing another planned explosion was made to the Begovaya station staff, but the caller soon revealed it to be a hoax.

[42] According to Interfax news agency, citing law enforcement sources, surveillance cameras captured two women – aged between 18 and 20 – boarding the metro at the Yugo-Zapadnaya station.

They opine that the attackers intended to blow up the Lubyanka station, which is located next to central headquarters of FSB, and then Oktyabrskaya, which is attached to the Ministry of Internal Affairs.

According to preliminary reports, law enforcement were notified about possible terror acts through three telegrams indicating potential threats to Moscow's transport system, but the suicide bombers passed through the security.

Unofficial reports the morning before the attacks took place indicate many female passengers of North Caucasian appearance were stopped and checked by Moscow security enforcement under pretence of routine ID verifications, and taken to local precincts.

[49][50] Russia's FSB security service have named the suicide bomber behind the Park Kultury metro station explosion[51] as Dzhanet Abdullayeva (1992–2010), "black widow" who had lived in the Khasavyurtsky region of Dagestan.

[52] Investigators confirmed that the second attacker was Maryam Sharipova, a 28-year-old schoolteacher from Dagestan, after her father identified her body[53] although he claimed she had a degree in mathematics and psychology and taught computer science while never expressing any "radical beliefs".

[51] Moscow said that there were an additional twenty-one "black widows" ready to strike, and were studying if the alleged attackers were part of an original group of thirty.

However, the attack followed a warning from Chechen rebel leader Doku Umarov the prior month of his intent to spread the Caucasian insurgency to Russian cities.

[55] Two days following the blasts, in a video message posted on a Chechen rebel website, Umarov claimed that his group was behind the bombings and that he had ordered the attacks.

Both these operations were accomplished by my order [...] And today, any politician, any journalist, any person that would condemn these operations, accuse me of terrorism, I laugh to his face, I only grin[...]On May 13, FSB director Aleksandr Bortnikov announced that they had identified all members of the group behind the attack and that three of the members were killed during a raid in an attempt to detain them, one of them being the person who escorted the suicide bombers from Dagestan to Moscow.

[citation needed] Bortnikov was quoted as saying: "To our great regret, we were unable to detain them alive because they put up fierce armed resistance and were killed.

Outside Russia, the United States increased security and police presence on transit systems in New York City, Washington, D.C., Chicago, and Atlanta following the attacks.