Russian authorities said Friday they had posthumously stripped the suspected Saint Petersburg metro suicide bomber of his citizenship.
The interior ministry said in a statement that 22-year-old suspected suicide bomber Akbarjon Djalilov, a Russian national born in Central Asian Kyrgyzstan, had posthumously been stripped of his Russian citizenship.
Djalilov's father has also been deprived of his Russian citizenship because he provided false information on his application, the ministry said.
The move comes as Russia raises the possibility of taking away the passports of naturalised citizens accused of involvement with the Islamic State jihadist group.
No one has claimed responsibility for the Saint Petersburg attack, but the authorities said they are probing ties to IS jihadists, who have threatened to strike Russia in revenge for its intervention in Syria.
Earlier Friday a woman injured in the bombing died in hospital, taking the death toll from the attack to 15.
The region's deputy 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 a serious condition, she said.
Ten men from Central Asia have been detained in connection with the bombing, including Kyrgyz-born Abror Azimov, who officials say was one of the organisers.
Both he and his elder brother Akram -- who the FSB security service alleges was in contact with global terror groups -- are in custody.
FSB head Alexander Bortnikov told reporters on Thursday that the agency was close to establishing who ordered the bombing, Russian news agencies reported.