Deputy regional governor Anna Mityanina said a woman born in 1960 had died from serious injuries sustained in the April 3 blast which ripped through an underground train.
Another 23 people are still in hospital, four of them in serious condition, she said.
Authorities say the attack was carried out by 22-year-old suicide bomber Akbarjon Djalilov, a Russian national born in Kyrgyzstan.
Ten men from Central Asia have been detained in connection with the bombing, including Kyrgyz-born Abror Azimov, whom officials say was one of the organisers.
There has been no claim of responsibility but investigators are looking into possible links to Islamic State jihadists, who have threatened to strike Russia in revenge for its intervention in Syria.
FSB head Alexander Bortnikov told reporters on Thursday that the agency was close to establishing who ordered the bombing, Russian news agencies reported.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)