A man killed two and injured nine more with a knife in northeast Moscow on Friday afternoon, a medical source said.
Police earlier said one woman succumbed to her injuries in hospital, where all the victims had been taken.
"Another woman died in hospital, where she was taken after the attack" the medical source said.
A five-year-old boy also received medical treatment for shock after witnessing the incident.
The suspect was detained some 15 minutes after the attack. The man, 27-year-old Alexei Arbuzov, was registered with a psychiatric clinic in his home town of Shatura, some 70 miles east of Moscow.
